As filed with the Securities and Exchange Commission on April 12, 2002
                                                     Registration No. 333-_____

                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549
                           - - - - - - - - - - - - - -
                                    FORM S-3
                             REGISTRATION STATEMENT
                                      UNDER
                           THE SECURITIES ACT OF 1933
                           - - - - - - - - - - - - - -
                            IGEN INTERNATIONAL, INC.
             (Exact Name of Registrant as Specified in Its Charter)

             DELAWARE                                       94-28528543
(State or Other Jurisdiction of                 (I.R.S Employer Identification
Incorporation or Organization)                              Number)

              16020 Industrial Drive, Gaithersburg, Maryland 20877
                                 (301) 869-9800
    (Address, Including Zip Code, and Telephone Number, Including Area Code,
                  of Registrant's Principal Executive Offices)

                              Samuel J. Wohlstadter
                 Chairman of the Board & Chief Executive Officer
                            IGEN International, Inc.
              16020 Industrial Drive, Gaithersburg, Maryland 20877
                                 (301) 869-9800
 (Name, Address, Including Zip Code, and Telephone Number, Including Area Code,
                              of Agent for Service)

                                 With a copy to:
                           Thomas F. Cooney, III, Esq.
                           Kirkpatrick & Lockhart LLP
             1800 Massachusetts Avenue, N.W., Washington, D.C. 20036

                  APPROXIMATE DATE OF COMMENCEMENT OF PROPOSED
        SALE TO THE PUBLIC: At any time and from time to time after this
                    Registration Statement becomes effective.

         If the only securities being registered on this Form are being offered
pursuant to dividend or interest reinvestment plans, please check the following
box. / /

         If any of the securities being registered on this Form are to be
offered on a delayed or continuous basis pursuant to Rule 415 under the
Securities Act of 1933 other than securities offered only in connection with
dividend or interest reinvestment plans, check the following box. /X/


         If this Form is filed to register additional securities for an offering
pursuant to Rule 462(b) under the Securities Act, please check the following box
and list the Securities Act registration statement number of the earlier
effective registration statement for the same offering. / /

         If this Form is a post-effective amendment filed pursuant to Rule
462(c) under the Securities Act, check the following box and list the Securities
Act registration statement number of the earlier effective registration
statement for the same offering. / /

         If delivery of the prospectus is expected to be made pursuant to Rule
434, please check the following box. / /




                         CALCULATION OF REGISTRATION FEE

Title of Each Class of                         Amount to be    Proposed Maximum       Proposed Maximum          Amount of
Securities to be Registered                     Registered    Offering Price per     Aggregate Offering      Registration Fee
                                                                   Share (1)              Price (1)
                                                                                                     
Common Stock, $ .001 par value                    31,726            $36.875             $1,169,896.25            $107.63
Series A Preferred Share Purchase Rights          31,726      Not applicable (2)     Not applicable (2)     Not applicable (2)
-----------------------------------------------------------------------------------------------------------------------------------


(1) Estimated solely for the purpose of calculating the registration fee
pursuant to Rule 457(c) of the Securities Act of 1933 based upon the average of
the high and low closing prices of the Registrant's Common Stock as reported on
the Nasdaq National Market on April 10, 2002.

(2) IGEN Common Stock includes associated rights (the "Rights") to purchase
shares of IGEN Series A Preferred Stock, par value $.001 per share. Until the
occurrence of certain prescribed events, none of which has occurred, the Rights
are not exercisable, are evidenced by the certificates representing IGEN Common
Stock and will be transferred along with and only with the IGEN Common Stock.
The value attributable to such Rights, if any, is reflected in the market price
of IGEN Common Stock.

THE REGISTRANT HEREBY AMENDS THIS REGISTRATION STATEMENT ON SUCH DATE OR DATES
AS MAY BE NECESSARY TO DELAY ITS EFFECTIVE DATE UNTIL THE REGISTRANT SHALL FILE
A FURTHER AMENDMENT WHICH SPECIFICALLY STATES THAT THIS REGISTRATION STATEMENT
SHALL THEREAFTER BECOME EFFECTIVE IN ACCORDANCE WITH SECTION 8(a) OF THE
SECURITIES ACT OF 1933 OR UNTIL THE REGISTRATION STATEMENT SHALL BECOME
EFFECTIVE ON SUCH DATE AS THE COMMISSION, ACTING PURSUANT TO SAID SECTION 8(a),
MAY DETERMINE.

                                       2


PROSPECTUS

Subject to Completion, dated April 12, 2002


                                  31,726 Shares

                            IGEN INTERNATIONAL, INC.

                                  COMMON STOCK


         The 31,726 shares of Common Stock of IGEN International, Inc. ("IGEN")
offered through this prospectus will be sold by the selling stockholder listed
on page 24 of this prospectus.

         The sale of shares offered through this prospectus may be effected by
the selling stockholder from time to time in transactions on the Nasdaq National
Market, in privately negotiated transactions or in a combination of such methods
of sale. The shares may be sold at fixed prices that may change, at prices
prevailing at the time of sale, at prices relating to such prevailing prices or
at negotiated prices. None of the proceeds from this offering will be received
by IGEN.

         IGEN's Common Stock is currently listed on the Nasdaq National Market
under the trading symbol "IGEN." IGEN's principal executive offices are located
at 16020 Industrial Drive, Gaithersburg, Maryland 20877. IGEN's telephone number
is (301) 869-9800.

         Potential investors should consider carefully the risk factors
beginning on page 5 of this prospectus.

         Neither the Securities and Exchange Commission nor any state securities
commission has approved or disapproved of these securities or determined if this
prospectus is truthful or complete. Any representation to the contrary is a
criminal offense.

         The information in this prospectus is not complete and may be changed.
The selling stockholder may not sell its shares PURSUANT TO THE REGISTRATION
STATEMENT until the registration statement filed with the Securities and
Exchange Commission is effective. This prospectus is not an offer to sell these
securities and it is not soliciting an offer to buy these securities in any
state where the offer or sale is not permitted.

                  The date of this prospectus is ________, 2002



                                       3




                                TABLE OF CONTENTS

About IGEN................................................................4
The Offering..............................................................5
Risk Factors..............................................................5
This Prospectus Includes Forward-Looking Information.....................21
Where to Find More Information...........................................22
Incorporation of Documents by Reference..................................22
Selling Stockholder......................................................24
Use of Proceeds..........................................................25
Plan of Distribution.....................................................25
Legal Matters............................................................26
Experts..................................................................26
Indemnification..........................................................26


         You should rely only on the information contained in this prospectus.
We have not authorized anyone to provide you with information different from
that contained in this prospectus. This prospectus is not an offer to sell or a
solicitation of an offer to buy Common Stock in any jurisdiction where it is
unlawful. The information contained in this prospectus is accurate only as of
the date of this prospectus, regardless of the time of delivery of this
prospectus or of any sale of Common Stock. This preliminary prospectus is
subject to completion prior to this offering.

         Origen, M-Series and Tricorder are trademarks owned by or licensed to
Igen International, Inc. Other trademarks and trade names appearing in this
prospectus are the property of their holders. The domain name and website
address www.igen.com, and all rights thereto, are registered in the name of and
owned by IGEN. The information on our website is not intended to be a part of
this prospectus.

                                   ABOUT IGEN

         We develop and market products that incorporate our proprietary
ORIGEN(R) technology, which permits the detection and measurement of biological
substances. We believe that ORIGEN offers significant advantages over competing
detection methods by providing a unique combination of speed, sensitivity,
flexibility and throughput in a single technology platform. ORIGEN is
incorporated into instrument systems and related consumable reagents, and we
also offer assay development and other services used to perform analytical
testing. Products based on our ORIGEN technology have been developed and sold
for the life science, clinical testing and industrial testing markets.

         We and our corporate collaborators have commercialized numerous product
lines to serve these markets. These sales and placements have been made
predominantly through our license arrangement with Roche Diagnostics GmbH
("Roche"), a leading provider of clinical diagnostic products.

                                       4


         We sell the M-SERIES(TM) System product line for use by pharmaceutical
and biotechnology companies in drug discovery and development. The M-SERIES
System may be used in all phases of drug discovery, including (1) validating
targets identified through genomics, (2) screening of large numbers of compounds
generated through combinatorial chemistry, (3) re-testing and optimization of
lead compounds, and (4) clinical trial testing of drug candidates. We also
provide custom assay development services. We market the M-SERIES System through
our sales, marketing and applications team dedicated to the life science market.

         We have also applied our ORIGEN technology to the rapidly growing
market for testing food and water for disease causing pathogens.

         Our address is 16020 Industrial Drive, Gaithersburg, Maryland 20877,
and our telephone number is (301) 869-9800.

                                  THE OFFERING

         This prospectus relates to 31,726 shares of Common Stock that may be
offered for sale by the selling stockholder. On March 26, 2002, we closed a
private placement of the Common Stock to an accredited investor. As part of the
private placement, we entered into a registration rights agreement with the
investor with respect to the purchased shares. We are registering the Common
Stock covered by this prospectus to fulfill our contractual obligations with
respect to these registration rights. Registration of the Common Stock does not
necessarily mean that all or any portion of such stock will be offered for sale
by the selling stockholder.

         We have agreed to bear the expenses of the registration of the Common
Stock under Federal and state securities laws, but we will not receive any
proceeds from the sale of the Common Stock offered under this prospectus.

                                  RISK FACTORS

         INVESTING IN OUR COMMON STOCK IS VERY RISKY. YOU SHOULD BE ABLE TO BEAR
A COMPLETE LOSS OF YOUR INVESTMENT. YOU SHOULD CAREFULLY CONSIDER THE FOLLOWING
FACTORS IN ADDITION TO OTHER INFORMATION CONTAINED ELSEWHERE IN THIS PROSPECTUS
OR INCORPORATED BY REFERENCE INTO THIS PROSPECTUS FROM OUR OTHER SEC FILINGS.
THE RISKS AND UNCERTAINTIES BELOW ARE NOT THE ONLY ONES FACING IGEN BECAUSE WE
ARE ALSO SUBJECT TO ADDITIONAL RISKS AND UNCERTAINTIES NOT PRESENTLY KNOWN TO
US. IF ANY OF THESE RISKS ACTUALLY OCCURS, OUR BUSINESS, FINANCIAL CONDITION,
OPERATING RESULTS, CASH FLOWS AND THE TRADING PRICE FOR OUR STOCK COULD BE
HARMED.

                                       5


         IF THE COMPANIES THAT LICENSE TECHNOLOGY FROM US DO NOT EFFECTIVELY
DEVELOP AND MARKET PRODUCTS BASED ON THAT TECHNOLOGY, OUR REVENUE WOULD BE
ADVERSELY AFFECTED.

         The success of our business depends, in large part, on how effectively
the companies to which we have licensed our technology develop and market that
technology. If these companies do not effectively develop and market products
based on this technology, our revenues would decrease.

         We have licensed our technology to Organon Teknika B.V., Eisai Co.,
Ltd., and Roche Diagnostics GmbH for selected markets and uses. Our license
agreements with each of these companies allow each company to develop products
using our technology and to manufacture and sell those products in selected
markets. In return for the right to use our technology, each of these companies
must pay royalties to us based on revenues they receive from sales of products
based on our technology. These royalties are a significant part of our overall
revenue. For example, they accounted for 52% of our revenue in fiscal year 2001.

         We believe that the companies licensing our technology have economic
incentives to continue marketing products using our technology. However, we
cannot be sure that these companies will diligently and effectively market
products that incorporate the technology we have licensed to them. In addition,
we have brought a lawsuit against Roche, one of our licensees, in part because
we believe Roche has not properly calculated and paid royalties to us and
because we believe Roche has not commercialized our technology as diligently as
our license agreement with Roche requires. See the risk factor immediately below
for a more detailed description of this litigation and the risks it poses to us.
We cannot predict whether similar or other problems will arise with other
companies to whom we license our technology.

         WE ARE SUING THE LARGEST LICENSEE OF OUR TECHNOLOGY, AND THE OUTCOME OF
THAT LITIGATION COULD MATERIALLY ADVERSELY AFFECT OUR REVENUES AND FINANCIAL
CONDITION.

         We have an ongoing lawsuit against Roche, which is the largest licensee
of our technology in terms of royalty income accounting for over 90% of our
royalty income in fiscal 2001. The lawsuit centers on a number of claims we
asserted against Roche in which we allege that they failed to comply with the
terms of our license agreement with them. Under the license agreement, we
granted Roche the exclusive right to manufacture, market and sell
immunodiagnostic products using our patented ORIGEN technology to a designated
field. The license restricts Roche's rights in the Japanese clinical diagnostic
market.

         In February 2002, the United States District Court issued a final order
of judgment in our case against Roche that awarded us $105 million in
compensatory damages and $400 million in punitive damages, confirmed our right
to terminate the Roche license agreement, and directed and commanded Roche to
grant to us for use in our retained fields a license to all improvements
developed by Roche under the agreement, including Roche's Elecsys(R) diagnostics
product line.

                                       6


         The judgment also bars Roche from marketing, selling, placing or
distributing outside of its licensed field any products, including its Elecsys
diagnostics product line, that are based on our ORIGEN(R) technology. We have
voluntarily agreed not to terminate the license agreement until an appellate
court determines that we are entitled to do so. We have already notified Roche
that the license agreement will terminate automatically once the judgment is
affirmed by the Court of Appeals. Once the agreement is terminated, Roche will
be prohibited from commercializing all ORIGEN-based products, including its
Elecsys diagnostics product line, and we will be free to operate, either
independently or with new partners, in the field currently licensed to Roche. We
cannot provide any assurance that we will ultimately prevail in this litigation.
If we do not succeed, our business and revenues could be materially adversely
affected.

         Roche has filed a counterclaim against us in the lawsuit, alleging,
among other things, that we breached the Roche license by permitting Eisai Co.,
Ltd., another of our licensees, to market some ORIGEN-based products in Japan.
The final judgment issued in this case found in our favor and against Roche on
all of Roche's counterclaims, except for one in which we were ordered to pay
$500,000.

         Roche has filed post judgment motions with the district court to set
aside certain aspects of the judgment and we expect that Roche will appeal the
judgment, if not overturned by the district court. During an appeal process,
which we expect to be completed in mid-2003, Roche is obligated to continue to
comply with the terms of the license agreement, including its obligation to
continue to pay us royalties on Roche's sales of royalty-bearing products.

         While we intend to vigorously oppose any appeal filed by Roche, there
can be no assurance that the judgment will not be overturned in whole or in part
or that the district court or an appellate court will not order a new trial on
some or all of the issues in the case. The risks involved in the litigation
include:

     -    The district court or an appellate court may modify or overturn some
          or all of the judgment favorable to us including the finding that
          Roche materially breached the license agreement, the scope and extent
          of the improvements awarded to us, the amount of compensatory and
          punitive damages, or the favorable findings relating to Roche's
          counterclaims against us.

     -    The district court or an appellate court could overturn some or all of
          the judgment and order a new trial on those issues.  For example, if
          the court orders a new trial on whether or not Roche miscalculated and
          underpaid royalties, breached its duty of good faith and fair dealing,
          or engaged  in unfair competition against us, the amount of damages
          awarded in a new trial could be lower than the amount already  awarded
          to us.

     -    If the court orders a new trial on any of the issues, we might need to
          continue expending significant amounts of money and management time in
          pursuing our claims  against Roche.  This time and money will then be
          unavailable for use in the development of our business.

                                       7


     -    If the  appellate  court  upheld the judgment that Roche materially
          breached the license agreement, and the license agreement were
          terminated, our royalty revenues would suffer unless and until we were
          able to introduce new products and generate revenues on our own or
          find one or more comparable replacements for Roche.

          There are no assurances that we could find a suitable replacement
          for Roche or successfully introduce new products on our own following
          termination of the license. Our ability to successfully commercialize
          new products, including products based on the improvements awarded to
          us in this litigation, is subject to numerous risks and uncertainties
          including risks relating to:

          -    the need for governmental approvalS;

          -    our ability to compete effectively;

          -    our ability to effectively manufacture and market new products;

          -    our ability to attract and retain employees;

          -    our need for additional financing;

          -    our dependence on suppliers; and

          -    the other risks applicable to our business as more completely
               described below and in our filings with the SEC.

     -    While an appeal is pending, Roche may divert its attention from
          selling the licensed products that generate royalties to us and focus
          its energies instead to find alternative products to develop and
          market.

     -    While an appeal is pending, Roche may continue to market and sell
          other Roche products that compete with its ORIGEN-based products,
          thereby lowering the royalty revenues that we would have otherwise
          received if Roche had sold more ORIGEN-based products instead of its
          other competing products.

 OUR ROYALTY INCOME COULD SUFFER AS A RESULT OF OUR LITIGATION AGAINST HITACHI.

         We are suing Hitachi Ltd. in Japan. Hitachi develops and manufactures
diagnostic equipment based on ORIGEN technology for Roche, to whom we license
our technology. We believe that Hitachi's actions in Japan violate rights that
we originally granted to Eisai Co., Ltd. to develop, manufacture and sell
products using ORIGEN technology to the Japanese clinical diagnostic market. We
have asked the Japanese court to prohibit Hitachi from manufacturing, using or
selling in Japan the Elecsys 2010 Instrument, which Hitachi developed for Roche
based on our technology.

                                       8


         If we lose our lawsuit against Hitachi and Hitachi continues Japanese
manufacturing of products covered by our license with Eisai, Eisai's ability to
sell products based on our technology in Japan could suffer, and the royalty
income we receive from Eisai could decrease as a result. If, on the other hand,
we win the lawsuit against Hitachi, Roche will either have to find a new
manufacturer to make equipment based on ORIGEN technology or make arrangements
for Hitachi to manufacture the equipment outside of Japan. Our royalty income
could suffer if Roche cannot effectively make alternate arrangements.

         In connection with our ongoing litigation against Roche, Roche has
attempted to sue us for interfering with its contract with Hitachi because we
filed this lawsuit. That claim was dismissed by the district court. If we lose
our lawsuit against Hitachi, Roche may try to bring this claim against us again.
There can be no assurance that we will be able to successfully dismiss this
claim if reinstated.

         FAILURE TO MEET OUR DEBT OBLIGATIONS COULD ADVERSELY AFFECT OUR RESULTS
OF OPERATIONS AND FINANCIAL CONDITION; IN ADDITION, OUR DEBT SERVICE OBLIGATIONS
COULD IMPAIR OUR OPERATING FLEXIBILITY.

         We have a substantial amount of indebtedness, and there is a
possibility that we may be unable to generate cash or arrange financing
sufficient to pay the principal of, interest on and other amounts due in respect
of our indebtedness when due, or in the event any of our indebtedness is
accelerated. In addition, our substantial leverage may require that we dedicate
a substantial portion of our expected cash flow from operations to service our
indebtedness, which would reduce the amount of our expected cash flow available
for other purposes, including working capital and capital expenditures.

         In March 1999, we entered into a debt financing with John Hancock
Mutual Life Insurance Company under a note purchase agreement in which we
received $30 million, and we issued 8.5% senior secured notes due 2006.
Principal and interest installments of $1.7 million are due quarterly through
March 2006. The notes are secured by, among other things, royalty payments and
our right to receive monies due under our license agreement with Roche and a
restricted cash balance account. If we are unable to meet our obligations under
the notes, the note holders could require us to repay the principal amount of,
and accrued interest on, the subordinated convertible debentures, and we may not
have sufficient financial resources or be able to arrange sufficient financing
to make those payments when required.

         In addition, covenants in the note purchase agreement for our 8.5%
senior secured notes require us to comply with annual and quarterly royalty
payment coverage ratios that are tied to royalty payments and debt service.
Termination of the license agreement with Roche would cause the debt payment
obligations to accelerate. This would reduce our cash on hand for other
purposes, including working capital and capital expenditures. There can be no
assurances that we will have sufficient capital to pay the debt, if accelerated
on termination of the license agreement or for any other reason. The note
purchase agreement also contains covenants that limit our ability to take
specified actions, including incurring additional secured debt and amending our
license agreement with Roche, which could affect our ability to resolve issues
that are being litigated through an


                                       9


amendment to the existing license agreement with Roche. These restrictions may
limit our operating flexibility, as well as our ability to raise additional
capital.

         In January 2000, we sold $35 million in aggregate principal amount of
5% subordinated convertible debentures due 2005. Unless and until holders of the
debentures convert their debentures into Common Stock, we are required to make
semi-annual interest payments of $875,000 through 2005. If we are unable to meet
our obligations under the subordinated convertible debentures, the debenture
holders could require us to repay the principal amount of, and accrued interest
on, the subordinated convertible debentures, and we may not have sufficient
financial resources or be able to arrange sufficient financing to make those
payments when required.

         WE HAVE A HISTORY OF OPERATING LOSSES, EXPECT TO INCUR FUTURE LOSSES
AND CANNOT BE CERTAIN THAT WE WILL BECOME A PROFITABLE COMPANY.

         We have experienced significant operating losses in most years since
our inception, and we expect those losses to continue. We also have an
accumulated deficit and negative net worth. Our losses have resulted principally
from costs incurred in research and development and from litigation costs,
selling costs and other general and administrative costs. We expect to incur
additional operating losses as a result of increases in expenses for
manufacturing, marketing and sales capabilities, litigation costs and expenses,
research and product development, the transfer and commercialization of
improvements from Roche, general and administrative costs and our share of
losses in Meso Scale Diagnostics ("MSD"). We cannot assure you that we will ever
achieve profitability in the future. Our ability to become profitable in the
future will depend on, among other things, our ability to:

     -    expand the commercialization of our existing products;

     -    upgrade and enhance the M-SERIES product capabilities;

     -    introduce new products into the market, including products for the
          markets currently served by Roche following termination of Roche's
          license with us;

     -    develop our marketing capabilities cost-effectively;

     -    develop sales and distribution capabilities cost-effectively; and

     -    establish successful collaborations with corporate partners to develop
          and commercialize products that incorporate our technologies.

         OUR QUARTERLY OPERATING RESULTS MAY FLUCTUATE SIGNIFICANTLY, AND THESE
FLUCTUATIONS MAY CAUSE OUR STOCK PRICE TO FALL.

         Our quarterly operating results depend upon:

                                       10


     -    the volume and timing of orders for M-SERIES or other products;

     -    the timing of instrument deliveries and installations;

     -    the success of M-SERIES upgrades and enhancements;

     -    variations in revenue recognized from royalties and other contract
          revenues;

     -    our mix of products sold;

     -    whether our instruments are sold to or placed with customers;

     -    the timing of our introduction of new products;

     -    our competitors' introduction of new products;

     -    variations in expenses we incur in connection with the operation of
          our  business, including costs associated  with  the  transfer  of
          improvements from Roche to us, research and development costs
          including costs associated with developing and commercializing new
          products for the markets currently served by Roche, and sales and
          marketing costs, including costs for upgrading the M-SERIES products;

     -    our share of losses in MSD;

     -    our manufacturing capabilities; and

     -    the volume and timing of product returns and warranty claims.

         These factors may cause our quarterly operating results to fluctuate
significantly, which in turn, may cause our stock price to fall. In addition,
because our revenues and operating results are volatile and difficult to
predict, we believe that period-to-period comparisons of our results of
operations are not a good indication of our future performance.

         WE MAY NOT BE ABLE TO RAISE SUFFICIENT ADDITIONAL CAPITAL TO
SUCCESSFULLY DEVELOP OUR BUSINESS.

         We need substantial amounts of money to fund our operations. We
currently anticipate that our existing capital resources, together with revenue
from product sales and royalties, will be adequate to fund our operations
through at least the end of our fiscal year ending March 31, 2003. Our access to
funds could be negatively impacted by many factors, including the results of
pending litigation, the volatility of the price of Common Stock, continued
losses from operations, acceleration of debt payment obligations resulting from
termination of the license agreement with Roche and other factors.

         We may need to raise substantial amounts of money to fund a variety of
future activities integral to the development of our business, including the
following:

                                       11


     -    for research and development in order to successfully develop our
          technologies, including to develop new products for the clinical
          diagnostic markets that are currently being served by Roche;

     -    to obtain regulatory approval for some of our products;

     -    to file and prosecute patent applications in order to protect our
          technologies;

     -    to respond to innovations that our competitors develop;

     -    to continue to aggressively pursue our ongoing litigations against
          Roche and Hitachi;

     -    to retain qualified employees, particularly in light of intense
          competition for qualified scientists and engineers;

     -    to make new arrangements to market our technology, including for the
          markets currently being served by Roche following the termination of
          our license agreement with Roche;

     -    to continue to fund investments in MSD;

     -    to manufacture products ourselves or through a third party; and

     -    to market different products to different markets, either through
          building our own sales and distribution capabilities or relying on a
          third party.

         We cannot be certain that we will have access to enough funds to
successfully develop our business.

         We may try to raise necessary additional capital by issuing additional
debt or equity securities. Holders of debt securities would have priority over
our equity holders with respect to the proceeds from the sale of our assets in
the event of liquidation of our business, and any debt financings we obtain may
contain restrictive terms that limit our operating flexibility. If, on the other
hand, we raise additional capital by selling more common or preferred stock, the
holdings of existing stockholders would be diluted. In December, 2001, we sold
1,062,947 shares of Common Stock at a purchase price of $29.45 per share; and in
March, 2002, we sold 1,031,726 shares of Common Stock at a purchase price of
$36.81 per share.

         If we are unable to raise additional capital, we may have to scale
back, or even eliminate, some programs. Alternatively, we may have to consider
pursuing arrangements with other companies, such as granting licenses or
entering into joint ventures. These arrangements could require that we give up
substantial rights to technology or products.

                                       12


         WE MAY NOT BE ABLE TO COMPETE EFFECTIVELY AGAINST MORE ESTABLISHED
COMPANIES AND INSTITUTIONS, WHICH COULD ADVERSELY AFFECT OUR BUSINESS.

         We are a relatively young company in a highly competitive industry. We
compete against established companies and research and academic institutions,
and we expect this competition to intensify. Many of these companies and
institutions have one or more competitive advantages over us, including:

     -    more money to invest;

     -    greater expertise and resources in developing, manufacturing,
          marketing and selling products;

     -    a larger, more experienced workforce; and

     -    more experience in obtaining regulatory approval for clinical
          diagnostic products.

         As a result, we may not be able to compete successfully against our
current or future competitors. This could have a material adverse effect on our
business, financial condition and revenue.

         WE DEPEND ON CONTINUING PRODUCT DEVELOPMENT.

         The market for our products is characterized by rapidly changing
technology, evolving industry standards, the need for updated and effective
technology and new product introduction. Our future success will depend in part
upon our ability to enhance existing products and to develop and introduce new
or enhanced products. There can be no assurance that we will be able to avoid
the obsolescence of our products due to rapid technological change and evolving
industry standards. In general, the development of new or enhanced products is a
complex and uncertain process requiring the accurate anticipation of
technological and market trends as well as precise technological execution. We
have and may continue to experience design, development, implementation and
other difficulties that could delay or prevent our introduction of new or
enhanced products or affect the performance of existing products. These
difficulties and delays have caused, and may continue to cause, our expenses to
increase and our product sales to fluctuate.

         WE DEPEND ON HIGHLY TRAINED AND SKILLED EMPLOYEES AND MANAGEMENT, AND
WE CANNOT BE SURE THAT WE WILL BE ABLE TO ATTRACT AND RETAIN SUFFICIENT
PERSONNEL.

         We need to hire additional staff and to retain existing staff, both of
which are difficult in today's competitive marketplace. Because we are a
technology company, we depend heavily on scientists and engineers to develop
products and to build a successful business. Research and development efforts
could suffer if we are not able to hire and retain enough qualified scientists
and engineers.

                                       13


         We cannot be sure that we will succeed in our hiring and retention
efforts. We compete with other technology companies and research and academic
institutions for experienced scientists. Many of these companies and
institutions have greater resources than we do and thus may be in a better
position to attract desirable candidates.

         In addition to scientists, we will also need to hire managers as the
business grows. We will need managers who are able to address the need for
regulatory, manufacturing and marketing capabilities. If we are not able to hire
managers with these skills, or develop expertise in these areas, our business
prospects could suffer.

         WE DEPEND ON A LIMITED NUMBER OF SUPPLIERS FOR MATERIALS USED IN
MANUFACTURING OUR PRODUCTS, AND ANY INTERRUPTION IN THE SUPPLY OF THOSE
MATERIALS COULD HAMPER OUR ABILITY TO MANUFACTURE PRODUCTS AND MEET CUSTOMER
ORDERS.

         We depend on vendors to supply key materials that we use in our
products. Some of these materials are available only from limited sources. In
the event of a reduction in, interruption of, or degradation in the quality of
the supply of any of our required materials, or an increase in the cost of
obtaining those materials, we would be forced to locate an alternative source of
supply. If no alternative source were available or if an alternative source were
not available on a timely basis or at a reasonable cost or otherwise on
acceptable terms, our ability to manufacture one or more of our products would
be delayed or halted. Any changes in sources of supply may require additional
engineering or technical development in order to ensure consistent and
acceptable performance of the products. If any of these events occur, product
costs may increase, we might be unable to deliver products timely, we could lose
sales as well as customers, and our business would be significantly harmed as a
result.

         WE MUST OBTAIN FDA APPROVAL TO MARKET OUR CLINICAL DIAGNOSTIC PRODUCTS,
WHICH IS OFTEN COSTLY AND TIME CONSUMING, AND IF WE DO NOT OBTAIN THE NECESSARY
APPROVAL OUR BUSINESS PROSPECTS WOULD SUFFER.

         The FDA regulates many areas in which we conduct research and in which
we develop, produce and market products. In particular, we must obtain FDA
approval before we can market clinical diagnostic products such as those we are
currently developing for the patient care market. The approval process is often
costly and time consuming. In addition, we cannot assure you that we will be
successful in obtaining FDA approval for any of our clinical diagnostic
products, which would materially adversely affect our future prospects.

         In order to obtain FDA approval in the United States, we, or the
companies with whom we work, will need to either obtain pre-market application
approval or pre-market notification clearance from the FDA. In order to obtain
pre-market notification clearance, we must submit data from clinical trials
demonstrating that new clinical diagnostic systems are substantially equivalent
to diagnostic systems that the FDA has already approved. If a product is subject
to the substantial equivalence requirement, neither we, nor any of our licensees
can sell that system for clinical use in the United States until the FDA
determines that a new ORIGEN-based system is substantially


                                       14


equivalent to a previously approved system. Typically, the FDA review process
takes 90 days, but the FDA's review could take longer. In addition, we cannot
be sure that we will be able to demonstrate substantial equivalence for future
diagnostic systems.

         If we do not successfully demonstrate substantial equivalence, or if we
are required to obtain pre-market application approval as an initial matter, we
will have to conduct extensive clinical testing of these products, which could
take years to complete. Extensive testing could involve substantial additional
costs and might delay bringing clinical diagnostic products to market, weakening
our competitive position. If we fail to obtain FDA approval for new products
altogether, we will be unable to market our ORIGEN-based systems at all for
clinical use in the United States.

         WE ARE SUBJECT TO EXTENSIVE, ONGOING GOVERNMENT REGULATION, WHICH MAY
INVOLVE SIGNIFICANT COSTS AND MAY RESTRICT OUR ABILITY TO CONDUCT BUSINESS.

         We expect that we may need to spend a substantial amount of money to
comply on an ongoing basis with the regulations of the FDA and other government
agencies. Government agencies, such as the FDA and the Environmental Protection
Agency, regulate manufacturers of diagnostic products and the manufacturing
process itself. The costs of complying with governmental regulations and any
restrictions that government agencies might impose could have a significant
impact on our business. As we increase our manufacturing, these costs will
increase.

         Whether we manufacture products ourselves or contract with another
company to manufacture products based on our technology, the FDA will
continually review and periodically inspect the manufacturing process. If the
FDA were to discover a problem with our products, the manufacturing process or
the manufacturing facility, the FDA could place restrictions on these products
and on the manufacturer. For example, the FDA could require us to recall, or
even totally withdraw, a product from the market or close a manufacturing
facility. In addition to FDA regulations, the process of manufacturing products
is subject to a variety of environmental and safety laws and regulations,
including laws and regulations governing the use and disposal of hazardous
materials. If we fail to comply with these laws or regulations, our business and
financial condition could be materially adversely affected.

         WE HAVE LIMITED MANUFACTURING AND MARKETING EXPERIENCE, WHICH PUTS US
AT A COMPETITIVE DISADVANTAGE.

         We lack experience in large-scale manufacturing, which could hamper our
ability to manufacture existing products or new products that we develop. We
have two options to address this issue. First, we could expand our internal
ability to manufacture products. Second, we could contract with a third party to
manufacture for us products based on our technology. If, however, we are unable
to expand our own manufacturing capability or find a suitable manufacturer on
acceptable terms we may be unable to meet demand for existing products and could
be delayed in introducing new products to the market. Failure to meet demand for
existing products or delays in introducing new products could put us at a
competitive disadvantage and could harm our financial condition or our business
prospects.

                                       15


         We will also need to develop greater selling, marketing and
distribution capabilities. To market clinical diagnostic products directly to
customers, and not through a licensee, we need to develop a substantial sales
force with technical expertise. We also need to establish a distribution system
to support the sales force. Alternatively, we could license or contract with
another company to provide sales and distribution services for products, in much
the same way as we have done with Roche, Eisai and Organon Teknika. We cannot be
sure, however, that we will be able to develop a sufficient sales and
distribution force or that we will be able to find a suitable company to fill
that role for us.

         THE SUCCESS OF OUR BUSINESS DEPENDS ON PATENTS THAT WILL EXPIRE AND
THAT MUST BE ACTIVELY PURSUED AND PROTECTED.

         Our business depends heavily on patents that will expire over time and
may be challenged or circumvented by competitors. Patents allow us to prevent
others, for a time, from using our inventions to compete against us. Our
business success or failure will depend, in part, on our ability to obtain and
maintain adequate patent protection for the ORIGEN technology. We cannot be
certain that current patents or future patents will adequately protect our
technology from being used by our competitors.

         Because there is no consistent policy governing the scope of claims in
medical patents, patent protection is uncertain. Companies may, for example,
challenge and invalidate patents or circumvent valid claims in patents, all of
which could make it necessary for us to defend our patents in litigation.
Litigation over patents poses the following risks to our business:

     -    Litigation costs can be extremely high, which could drain our
          financial resources.

     -    Litigation  over our patents could discourage other companies from
          working with us to develop and market new products based on technology
          covered by these disputed patents.

     -    If we lose some patent protection as a result of litigation, our
          competitive advantage could be eroded.

         OUR BUSINESS WOULD BE HARMED IF WE VIOLATE THE PATENT RIGHTS OF OTHERS.

         Our business success or failure will also depend, in part, on the
patent rights of others. We license technology from other companies and academic
institutions. Because access to this technology is necessary to our business, we
must be certain that we comply with these license agreements. Our business could
be harmed if we breached any of these license agreements and lost the rights to
use this patented technology or if we were unable to renew existing licenses on
acceptable terms or get additional licenses that we may need on acceptable
terms.

         We must also make sure that we do not infringe the patent rights of
others. If we were to infringe others' patent rights we could be exposed to the
following risks:

                                       16


     -    We could be required to alter, or abandon, our products or processes.

     -    We could be required to obtain a license from the patent holder.

     -    We could lose customers that are reluctant to continue using our
          products or doing business with us.

     -    We could be forced to abandon development work that we had begun with
          respect to these products.

     -    We could be required to pay damages that could be substantial.

         We cannot be sure that we would be able to alter products or processes
or that we could obtain a license at a reasonable cost, if at all. Our business
could be damaged if we were unable to make necessary alterations or obtain a
necessary license on acceptable terms.

         In addition, we may need to litigate the scope and validity of patents
held by others and such litigation could be a substantial cost for us.

         WE RELY ON TRADE SECRETS AND OTHER INFORMATION THAT CANNOT BE PROTECTED
BY PATENTS, AND WE FACE RISKS THAT THIS INFORMATION WILL BE DISCLOSED TO OTHERS.

         In addition to patents, we also rely in our business on trade secrets,
know-how and other proprietary information. If this information were disclosed
to competitors, our business would suffer. We seek to protect this information,
in part, by entering into confidentiality agreements with licensees, employees
and consultants, which prohibit these parties from disclosing our confidential
information. Despite our entering into these agreements, we cannot be sure that
the agreements will provide adequate protection for our trade secrets, know-how
and other proprietary information or that the information we share with others
during the course of our business will remain confidential. We also cannot be
certain that we would have sufficient legal remedies to correct or compensate
for unauthorized disclosures or sufficient resources to seek redress.

         RESTRICTIONS ON HEALTH CARE COSTS AND HEALTH CARE AND INSURANCE
FINANCING PRACTICES COULD LIMIT DEMAND FOR OUR PRODUCTS.

         In the United States and elsewhere, demand for clinical diagnostic
testing is dependent, in part, on consumers' ability to be reimbursed for the
cost of the tests by third-party payors, such as government agencies, health
maintenance organizations and private insurers. Medicaid and other third-party
payors are increasingly challenging the prices charged for medical services,
including clinical diagnostic tests. They are also attempting to contain costs
by limiting their coverage of, and the amount they will reimburse for, clinical
diagnostic tests and other health care products . We cannot be certain that
insurers will provide coverage for clinical diagnostic tests in the future.
Without adequate coverage and reimbursement, consumer demand for clinical
diagnostic tests may decrease. Decreased demand would likely cause sales of our
clinical diagnostic products, and sales


                                       17


by our licensees, to fall since fewer tests would be performed or prices would
be lowered, or both. Reduced sales or royalty income would hurt our business
and our business prospects.

         In many foreign markets, governments directly set the prices that
clinical diagnostic companies may charge for their products and services. In the
United States, a number of legislative and regulatory proposals aimed at
changing the health care system have been proposed in recent years. We cannot
predict whether these proposals will be adopted or the effect that these
proposals or managed care efforts may have.

         WE ARE EXPOSED TO PRODUCT LIABILITY RISKS.

         We may not be able to adequately insure against risk of product
liability. As we begin marketing products, we may face product liability for
claims and lawsuits brought by customers. Damages awarded in product liability
cases can be very large. While we have product liability insurance, this
coverage is limited. We cannot assure you that our current product liability
insurance would be adequate to cover us against our potential liabilities or
that we will be able to maintain current levels of product liability insurance
on acceptable terms, if at all. Claims or losses in excess of our current or
future product liability insurance coverage could have a material adverse effect
on our financial condition.

         MANAGEMENT EXERCISES SIGNIFICANT CONTROL OVER IGEN.

         Our management has significant control over IGEN through its stock
ownership. Our officers and directors own, or have the right to purchase, about
28% of Common Stock and our Chief Executive Officer owns approximately 21% of
the Common Stock at March 11, 2002. Our officers and directors have significant
influence over the election of directors and other stockholders actions.

         FAILURE TO MANAGE OUR GROWTH COULD ADVERSELY AFFECT OUR BUSINESS.

         We have grown rapidly and expect to continue to grow by hiring new
employees in all areas of our operations, increasing our presence in existing
markets and introducing new products we develop into new potential high-growth
markets. Our growth has placed, and continues to place, a strain on our
management and our operating and financial systems.

         As we grow, our personnel, systems, manufacturing capabilities and
resources, procedures and controls may be inadequate to support future
operations. In order to accommodate the increased operations for sales and
marketing, research and development, facilities and administration, we will need
to hire, train and retain the appropriate personnel. We may also need to improve
our financial and management controls, reporting systems and operating systems.
We may encounter difficulties in developing and implementing other new systems.

         In response to our growth, we have recently implemented a new
enterprise resource planning system in order to automate all of our accounting,
manufacturing, sales and purchasing. If the enterprise resource planning system
fails to operate as we expect or experiences delays or


                                       18


interruptions, our operations, as well as our ability to manage our increased
growth, could be materially adversely affected.

 PROVISIONS OF OUR GOVERNING DOCUMENTS MAY DETER OTHERS FROM ATTEMPTING TO
ACQUIRE US.

         Our governing documents contain provisions designed to prevent hostile
takeovers, which may limit the ability of stockholders to sell their stock at a
premium in a takeover. According to our governing documents, stockholders can
only act at annual meetings or at special meetings of stockholders. Stockholders
are not allowed to act by written consent. In addition, stockholders are not
allowed to call for a special meeting. Only our board of directors, the chairman
of the board or the president may call a special meeting. These provisions may
make it difficult for stockholders to force us to hold special meetings. These
provisions may also limit the ability of stockholders to consider transactions
that they may want to approve, such as a hostile takeover of us.

         Our governing documents also contain other provisions that could make
it more difficult for a change in control to be effected. Our board of directors
can issue preferred stock and can determine the rights of those preferred
stockholders without the approval of holders of Common Stock. For example, our
board of directors could give preferred stockholders one or more votes on issues
on which holders of Common Stock vote. This could have the effect of diluting
the voting rights of holders of Common Stock, which might further discourage
other companies from trying to acquire us.

         In addition, our certificate of incorporation contains provisions
dividing our board of directors into three classes. Each class serves until the
third succeeding annual meeting, and one class is elected at each annual meeting
of stockholders. As a result, even if our stockholders might prefer to effect a
change sooner, it could take at least two annual meetings of stockholders to
change a majority of the members of the board of directors.

         Furthermore, our certificate of incorporation authorizes, and we have
adopted, a preferred share purchase rights plan, commonly referred to as a
"poison pill." Under the rights plan, we made a dividend distribution to the
stockholders of record on November 6, 1996 of one right to purchase from us one
one-hundredth of a share of our preferred stock for each outstanding share of
Common Stock. The terms of the rights and the circumstances under which they may
be exercised are contained in a rights agreement, which has been filed with the
SEC.

         These terms have been designed to deter hostile takeovers of us, even
though our stockholders might favor a takeover, especially if it were to afford
them an opportunity to sell their stock at a price above the prevailing market
rate.

   OUR STOCK PRICE IS VOLATILE AND COULD DROP PRECIPITOUSLY AND UNEXPECTEDLY.

         Our Common Stock currently trades on The Nasdaq National Market. The
prices of publicly traded stock often fluctuate. The price of our stock may rise
or fall dramatically, even though our


                                       19


business performance has not changed. In the past, the stock price of
technology companies has been especially volatile.  We expect that this will
continue to be the case.

         In addition to these fluctuations, an investment in our stock could be
affected by a wide variety of factors that relate to our business and industry,
many of which are outside of our control. For example, the value of Common Stock
could be affected by:

     -    new product introductions;

     -    innovations by competitors;

     -    our competitors' announcements of their financial results;

     -    the failure of our operating results to meet or exceed the
          expectations of investors and analysts;

     -    changes in financial estimates and recommendations by security
          analysts;

     -    general economic conditions;

     -    disputes over patents or other proprietary rights;

     -    new or existing litigation, including our litigation with Roche;

     -    publicity;

     -    regulations;

     -    market conditions; and

     -    fluctuations in our performance and the performances of our licensees.

         WE DO NOT PLAN TO PAY ANY CASH DIVIDENDS ON OUR COMMON STOCK.

         We have never paid cash dividends on Common Stock. We have no plans to
pay cash dividends in the foreseeable future.

         THE VALUE OF THE COMMON STOCK MAY BE DILUTED IN THE FUTURE.

         Our officers, directors, employees and consultants have options to
purchase a significant aggregate amount of Common Stock. If they exercise their
options and purchase Common Stock, Common Stock will be diluted. In addition, we
currently have preferred stockholders and convertible debenture holders who have
the right to convert their preferred shares and debentures, as the case may be,
to Common Stock. Common Stock would be diluted if these preferred stockholders
or convertible debenture holders decide to convert their securities in the
future. Moreover, Common Stock could be further diluted if we issue additional
Common Stock or


                                       20


securities convertible into Common Stock in the future, which we may need to do
to raise funds for our business. Sales of additional shares of Common Stock or
the conversion of securities into Common Stock could cause the market price of
Common Stock to decrease.

              THIS PROSPECTUS INCLUDES FORWARD-LOOKING INFORMATION

         This prospectus and the documents incorporated in this prospectus by
reference include forward-looking statements under the Securities Act. In
addition from time to time, we or our representatives have made or may make
forward-looking statements orally or in writing. The words "may," "will,"
"expect," "anticipate," "believe," "estimate," "plan," "intend" and similar
expressions have been used in this prospectus and the documents incorporated in
this prospectus by reference to identify forward-looking statements. We have
based these forward-looking statements on our current views with respect to
future events and financial performance. Actual results could differ materially
from those projected in the forward-looking statements. These forward-looking
statements are subject to risks, uncertainties and assumptions, including, among
other things:

     -    adverse results in our litigation with Roche;

     -    risks associated with managing and maintaining internal growth;

     -    competition, including market competition, competition in the patent
          process and our ability to consummate contract negotiations with
          prospective licensees;

     -    the possible termination of contracts with key licensees;

     -    changes in coverages or reimbursement practices of health maintenance
          organizations and private insurers;

     -    adverse results in other litigation and in regulatory matters, the
          adoption of adverse legislation or regulations, more aggressive
          enforcement of existing  legislation or regulations or a change in the
          interpretation of existing legislation or regulations;

     -    dependence on key members of management;

     -    other risks described in this "Risk Factors" section; and

     -    other risks described from time to time in our filings with the SEC.

         We are not obligated to update or revise any forward-looking
statements, whether as a result of new information, future events or otherwise.
All subsequent written and oral forward-looking statements attributable to us or
persons acting on our behalf are expressly qualified in their entirety by the
cautionary statements contained throughout this prospectus and the documents
incorporated in this prospectus by reference. Because of these risks,
uncertainties and assumptions, you should not place undue reliance on these
forward-looking statements.

                                       21


                         WHERE TO FIND MORE INFORMATION

         We are subject to the reporting requirements of the Securities Exchange
Act of 1934 and file annual, quarterly and current reports, proxy statements and
other information with the SEC. You may read and copy these reports, proxy
statements and other information at the SEC's public reference facilities at
Judiciary Plaza, 450 Fifth Street, N.W., Washington, D.C. 20549 and at Northwest
Atrium Center, 500 W. Madison Street, Suite 1400, Chicago, Illinois 60661-2511.
You can request copies of these documents by writing to the SEC and paying a fee
for the copying cost. Please call the SEC at 1-800-SEC-0330 for more information
about the operation of the public reference facilities. SEC filings are also
available at the SEC's Web site at http://www.sec.gov. Our Common Stock is
listed on the Nasdaq National Market, and you can read and inspect our filings
at the offices of the National Association of Securities Dealers, Inc. at 1735 K
Street, Washington, D.C. 20006.

         This prospectus is only part of a Registration Statement on Form S-3
that we have filed with the SEC under the Securities Act of 1933 and therefore
omits certain information contained in the Registration Statement. We have also
filed exhibits and schedules with the Registration Statement that are excluded
from this prospectus, and you should refer to the applicable exhibit or schedule
for a complete description of any statement referring to any contract or other
document. You may inspect a copy of the Registration Statement, including the
exhibits and schedules, without charge, at the public reference room or obtain a
copy from the SEC upon payment of the fees prescribed by the SEC.

                     INCORPORATION OF DOCUMENTS BY REFERENCE

         The SEC allows us to "incorporate by reference" information that we
file with them. Incorporation by reference allows us to disclose important
information to you by referring you to those other documents. The information
incorporated by reference is an important part of this prospectus, and
information that we file later with the SEC will automatically update and
supersede this information. We filed a Registration Statement on Form S-3 under
the Securities Act of 1933 with the SEC with respect to the Common Stock being
offered pursuant to this prospectus. This prospectus omits certain information
contained in the Registration Statement, as permitted by the SEC. You should
refer to the Registration Statement, including the exhibits, for further
information about us and the Common Stock being offered pursuant to this
prospectus. Statements in this prospectus regarding the provisions of certain
documents filed with, or incorporated by reference in, the Registration
Statement are not necessarily complete and each statement is qualified in all
respects by that reference. Copies of all or any part of the Registration
Statement, including the documents incorporated by reference or the exhibits,
may be obtained upon payment of the prescribed rates at the offices of the SEC
listed above. We incorporate by reference the documents listed below and any
future filings made with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the
Securities Exchange Act of 1934 until we sell all of our shares of Common Stock
covered by the registration statement. The documents we are incorporating by
reference are:

     -    Annual Report on Form 10-K for the year ended March 31, 2001;

                                       22


     -    Quarterly Reports on Form 10-Q for the quarters ended June 30,
          September 30 and December 31, 2001;

     -    Proxy Statement filed July 30, 2001;

     -    Supplement filed September 5, 2001 to the Proxy Statement filed July
          30, 2001;

     -    Current Report on Form 8-K, dated August 15, 2001;

     -    Amendment No. 1 to the Current Report on Form 8-K, dated August 15,
          2001;

     -    Current Report on Form 8-K, dated December 7, 2001;

     -    Current Report on Form 8-K, dated January 10, 2002;

     -    Current Report on Form 8-K, dated February 15, 2002;

     -    Current Report on Form 8-K, dated March 8, 2002; and

     -    The description of Common Stock contained in our Registration
          Statement on Form 8-A filed with the SEC on December 10, 1996
          including any amendments or reports filed for the purpose of updating
          such description.

         Upon request, we will provide without charge to each person to whom a
copy of this prospectus has been delivered a copy of any information that was
incorporated by reference in the prospectus (other than exhibits to documents,
unless the exhibits are specifically incorporated by reference into the
prospectus). We will also provide upon request, without charge to each person to
whom a copy of this prospectus has been delivered, a copy of all documents filed
by us from time to time with the SEC pursuant to the Securities Exchange Act of
1934. Requests for copies should be directed to:

                           IGEN International, Inc.
                           16020 Industrial Drive
                           Gaithersburg, MD  20877
                           Attention:  George Migausky, Chief Financial Officer
                           Telephone:  (301) 869-9800

         This prospectus is part of a Registration Statement we filed with the
SEC. You should rely only on the information incorporated by reference in or
provided in this prospectus and the Registration Statement. We have not
authorized any other person to provide you with different information. We are
not making an offer of these securities in any state where the offer is not
permitted. You should not assume that the information in this prospectus is
accurate as of any date other than the date on the front of this document.

                                       23


                               SELLING STOCKHOLDER

         As part of the private placement that we closed on March 26, 2002, we
entered into a registration rights agreement with the investor with respect to
the purchased shares. We are registering the Common Stock covered by this
prospectus to fulfill our contractual obligations with respect to these
registration rights.

         The following table sets forth the name of the stockholder selling
shares of Common Stock in this offering, the number of shares of Common Stock
owned by such selling stockholder as of April 3, 2002 and the number of shares
of Common Stock that may be offered for sale pursuant to this prospectus by such
selling stockholder. In some instances, the shares offered pursuant to this
prospectus may be sold by the pledgees, donees or transferees of or other
successors in interest to the selling stockholder. The selling stockholder has
not held any position, office or other material relationship with IGEN or any of
its affiliates within the past three years other than as a result of the
transactions that resulted in its ownership of shares of Common Stock.

         The shares may be offered from time to time by the selling stockholder
named below. However, the selling stockholder is under no obligation to sell all
or any portion of such shares, nor is the selling stockholder obligated to sell
any such shares immediately pursuant to the Registration Statement. Because the
selling stockholder may sell all or part of its shares, no estimate can be given
as to the number of shares of Common Stock that will be held by the selling
stockholder after termination of any offering made by this prospectus.




                      Common Stock Beneficially Owned After
                     Offering If All Offered Shares Are Sold
                                        Shares of Common Stock   Common Stock        Number           Percent of
                                          Beneficially Owned        Offered     of Shares Owned       Outstanding
Name of Selling                           Prior to Offering         Hereby       After Offering   Shares Owned After
Stockholder                                                                                            Offering
-------------------------------------- ------------------------- -------------- ----------------- --------------------
                                                                                             
Citadel Equity Fund Ltd.                      851,716(1)            31,726         819,990(1)            3.4%




     (1)  Includes as of April 3, 2002,  shares of Common  Stock  issuable  upon
          conversion  of  $25,000,000  aggregate  principal  amount  of  our  5%
          subordinated  convertible  debentures  due 2005 and  shares  of Common
          Stock which are not being  offered  pursuant to this  prospectus.

     (2)  Based on 23,062,192  shares issued and outstanding as of April 3, 2002
          and determined in accordance  with Section 13(d) of the Securities and
          Exchange Act of 1934, as amended.

         From time to time the selling stockholder may transfer or donate its
shares to others and upon acquiring the shares, such persons will be deemed to
be selling stockholders for purposes of this prospectus. The number of shares
owned by the selling stockholder in the event of such transfer or donation of
shares will decrease as and when it takes such actions. The plan of distribution
for shares sold hereunder will otherwise remain unchanged, except that the
transferees, donees or other successors will be selling stockholders hereunder.
If IGEN is notified by a selling


                                       24


stockholder that a transferee or a donee intends to sell more than 500 shares,
a supplement to this prospectus will be filed.

                                 USE OF PROCEEDS

         There will be no proceeds to IGEN from the sale of the shares by the
selling stockholder. Any proceeds from the sale of Common Stock received by the
selling stockholder will be retained by the selling stockholder.

         IGEN will pay substantially all of the expenses incident to the
registration, offering and sale of the shares to the public other than
commissions or discounts of underwriters, broker-dealers or agents and the
expenses of counsel to the selling stockholder. Such expenses are estimated to
be approximately $14,000. IGEN has also agreed to indemnify the selling
stockholder against certain liabilities, including liabilities under the
Securities Act of 1933.

                              PLAN OF DISTRIBUTION

         We are registering the shares of Common Stock on behalf of the selling
stockholder, and IGEN will not receive any proceeds from this offering. The
shares of Common Stock may be sold in one or more transactions at fixed prices,
at prevailing market prices at the time of sale, at prices related to the
prevailing market prices, at varying prices determined at the time of sale, or
at negotiated prices. These sales may be effected at various times in one or
more of the following transactions, or in other kinds of transactions:

     o    transactions on the Nasdaq National Market or on any national
          securities exchange or U.S. inter-dealer system of a registered
          national securities association on which the Common Stock may be
          listed or quoted at the time of sale;

     o    in the over-the-counter market;

     o    in private transactions and transactions otherwise than on these
          exchanges or systems or in the over-the-counter market;

     o    in connection with short sales of the shares;

     o    by pledge to secure debt and other obligations;

     o    through the writing of options, whether the options are listed on an
          options exchange or otherwise;

     o    in connection with the writing of non-traded and exchange-traded  call
          options, in hedge transactions and in settlement of other transactions
          in standardized or over-the-counter options; or

     o    through a combination of any of the above transactions, or by any
          other legally available means.

                                       25


         The selling stockholder and its successors, including their
transferees, pledgees or donees or their successors, may sell the Common Stock
directly to purchasers or through underwriters, broker-dealers or agents, who
may receive compensation in the form of discounts, concessions or commissions
from the selling stockholder or the purchasers. These discounts, concessions or
commissions as to any particular underwriter, broker-dealer or agent may be in
excess of those customary in the types of transactions involved.

         In addition, any securities covered by this prospectus which qualify
for sale pursuant to Rule 144 of the Securities Act may be sold under Rule 144
rather than pursuant to this prospectus.

         We entered into a registration rights agreement for the benefit of the
selling stockholder to register the Common Stock under applicable Federal and
state securities laws. The registration rights agreement provides for
cross-indemnification of the selling stockholder and us and our respective
directors, officers and controlling persons against specific liabilities in
connection with the offer and sale of the Common Stock, including liabilities
under the Securities Act. We will pay substantially all of the expenses incurred
by the selling stockholder incident to the offering and sale of the Common
Stock.

                                  LEGAL MATTERS

         The validity of the issuance of the Common Stock offered in this
prospectus is being passed upon for us by Kirkpatrick & Lockhart LLP.

                                     EXPERTS

         The consolidated financial statements incorporated in this prospectus
by reference from IGEN's Annual Report on Form 10-K for the year ended March 31,
2001 have been audited by Deloitte & Touche LLP, independent auditors, as stated
in their report, which is incorporated herein by reference and have been so
incorporated in reliance upon the report of such firm given upon their authority
as experts in accounting and auditing.

                                 Indemnification

         The Company's Bylaws provide that the Company shall indemnify its
directors and officers to the fullest extent not prohibited by the General
Corporation Law of the State of Delaware; provided, however, that the Company
may modify the extent of such indemnification by individual contracts with its
directors and officers; and, provided, further, that the Company shall not be
required to indemnify any director or officer in connection with any proceeding
(or part thereof) initiated by such person unless (i) such indemnification is
expressly required by law, (ii) the proceeding was authorized by the Board of
Directors of the Company, (iii) such indemnification is provided by the Company,
in its sole discretion, pursuant to the powers vested in the Company by the
General Corporation Law of the State of Delaware, or (iv) such indemnification
is otherwise required by law, by agreement, or by vote of the stockholders or
disinterested directors. Pursuant to these Bylaw provisions, the Company has
entered into indemnity agreements with each of its


                                       26


directors and executive officers and has obtained director and officer
liability insurance in the amount of $30,000,000.

         Section 145 of the General Corporation Law of the State of Delaware
permits a corporation, under specified circumstances, to indemnify its
directors, employees or agents against expenses (including attorney's fees),
judgments, fines and amounts paid in settlements actually and reasonably
incurred by them in connection with any action, suit or proceeding brought by
third parties by reason of the fact that they were or are directors, officers,
employees or agents of the corporation, if such directors, officers, employees
or agents acted in good faith and in a manner they reasonably believed to be in
or not opposed to the best interests of the corporation and, with respect to any
criminal action or proceeding, had no reason to believe their conduct was
unlawful. In a derivative action, i.e., one by or in the right of the
corporation, indemnification may be made only for expenses actually and
reasonably incurred by directors, officers, employees or agents in connection
with the defense or settlement of an action or suit, and only with respect to a
matter as to which they shall have acted in good faith and in a manner they
reasonably believed to be in or not opposed to the best interests of the
corporation, except that no indemnification shall be made if such person shall
have been adjudged liable to the corporation, unless and only to the extent that
the court in which the action or suit was brought shall determine upon
application that the defendant directors, officers, employees or agents are
fairly and reasonably entitled to indemnity for such expenses despite such
adjudication of liability.

         Article VI of the Company's Certificate of Incorporation states that
directors of the Company will not be personally liable to the Company or its
stockholders for monetary damages for any breach of fiduciary duty as a
director, except for liability (i) for any breach of the director's duty of
loyalty to the company or its stockholders, (ii) for acts or omissions not in
good faith or which involve intentional misconduct or a knowing violation of
law, (iii) under Section 174 of the General Corporation Law of the state of
Delaware, which makes directors liable for unlawful dividends or unlawful stock
repurchases or redemptions or (iv) for any transaction from which the director
derived an improper personal benefit. The Company's Certificate of Incorporation
further provides that if the General Corporation Law of the State of Delaware is
amended to authorize corporate action further eliminating or limiting the
personal liability of directors, then the liability of the Company's directors
shall be eliminated or limited to the fullest extent permitted by the General
Corporation Law of the State of Delaware, as so amended.

         We have not authorized any dealer, salesperson or other person to give
any information or represent anything not contained in this prospectus. You must
not rely on any unauthorized information. If anyone provides you with different
or inconsistent information, you should not rely on it. This prospectus does not
offer to sell any shares in any jurisdiction where it is unlawful. The
information in this prospectus is current as of the date shown on the cover
page.

                         [LOGO] IGEN International, Inc.

                          31,726 Shares of Common Stock
                 ----------------------------------------------
                                   PROSPECTUS
                 ----------------------------------------------



______________, 2002



                                       27




PART II. INFORMATION NOT REQUIRED IN PROSPECTUS

ITEM 14. OTHER EXPENSES OF ISSUANCE AND DISTRIBUTION

         The following table sets forth the Company's estimates (other than the
SEC and Nasdaq registration fees) of the expenses in connection with the
issuance and distribution of the shares of Common Stock being registered.




          ITEM                                             AMOUNT
                                                        
          SEC registration fee                               $108
                                                            -----
          Nasdaq listing fee                                  317
                                                            -----
          Legal fees and expenses                           5,000
                                                            -----
          Accounting fees and expenses                      7,000
                                                            -----
          Miscellaneous fees and expenses                   1,575
                                                            -----
                                                            --------

          Total                                             $14,000
                                                            ========


ITEM 15. INDEMNIFICATION OF DIRECTORS AND OFFICERS

         See "Indemnification" contained in Part I hereof, which is incorporated
herein by reference.

ITEM 16. EXHIBITS

         Exhibit
         Number        Description

         4.7           Form of Common Stock Certificate (Previously filed
                       and incorporated by reference to Registration
                       Statement on Form 8-A of the Company filed with the
                       Securities and Exchange Commission on December 10,
                       1996).

         5.1           Opinion of Kirkpatrick & Lockhart LLP regarding legality.

         23.1          Consent of Kirkpatrick & Lockhart LLP (see Exhibit 5.1).

         23.2          Consent of Deloitte & Touche LLP.

         24.1          Power of Attorney (included on signature page).

         -------------------------

                                       28


ITEM 17. UNDERTAKINGS

(a)      Rule 415 Offering.

         The undersigned registrant hereby undertakes:

         (1) To file, during any period in which offers or sales are being made,
a post-effective amendment to this registration statement:

          (i)  To include any  prospectus  required  by Section  10(a)(3) of the
               Securities Act of 1933;

          (ii) To reflect in the  prospectus  any facts or events  arising after
               the  effective  date of the  registration  statement (or the most
               recent post-effective  amendment thereof) which,  individually or
               in  the  aggregate,   represent  a  fundamental   change  in  the
               information   set   forth   in   the   registration    statement.
               Notwithstanding the foregoing, any increase or decrease in volume
               of  securities  offered (if the total dollar value of  securities
               offered  would not  exceed  that  which was  registered)  and any
               deviation  from  the low or  high  end of the  estimated  maximum
               offering  range may be reflected in the form of prospectus  filed
               with the Commission pursuant to Rule 424(b) if, in the aggregate,
               the  changes  in volume  and price  represent  no more than a 20%
               change in the maximum  aggregate  offering price set forth in the
               "Calculation  of  Registration   Fees"  table  in  the  effective
               registration statement;

          (iii)To include any material  information  with respect to the plan of
               distribution   not  previously   disclosed  in  the  registration
               statement  or any  material  change  to such  information  in the
               registration  statement.   Provided,   however,  that  paragraphs
               (a)(1)(i)  and  (a)(1)(ii)  do  not  apply  if  the  registration
               statement  is on  Form  S-3 or  Form  S-8,  and  the  information
               required to be included in a  post-effective  amendment  by those
               paragraphs  is  contained  in  periodic   reports  filed  by  the
               registrant  pursuant  to  Section  13 or  Section  15(d)  of  the
               Securities   Exchange  Act  of  1934  that  are  incorporated  by
               reference in the registration statement.

         (2) That, for the purpose of determining any liability under the
Securities Act of 1933, each such post-effective amendment shall be deemed to be
a new registration statement relating to the securities offered therein, and the
offering of such securities at that time shall be deemed to be the initial bona
fide offering thereof.

         (3) To remove from registration by means of a post-effective amendment
any of the securities being registered which remain unsold at the termination of
the offering.

(b)      Filings Incorporating Subsequent Exchange Act Documents by Reference.

         The undersigned registrant hereby undertakes that, for purposes of
determining any liability under the Securities Act of 1933, each filing of the
registrant's annual report pursuant to section 13(a) or section 15(d) of the
Securities Exchange Act of 1954 (and, where applicable, each filing of an
employee benefit plan's annual report pursuant to section 15(d) of the
Securities Exchange Act of 1934) that is incorporated by reference in the
registration statement shall be


                                       29


deemed to be a new registration statement relating to the securities offered
therein, and the offering of such securities at that time shall be deemed to be
the initial bona fide offering thereof.

(h)      Request for Acceleration of Effective Date.

         Insofar as indemnification for liabilities arising under the Securities
Act of 1933, may be permitted to directors, officers, and controlling persons of
the registrant pursuant to the provisions described in Item 15 or otherwise, the
registrant has been advised that in the opinion of the Securities and Exchange
Commission, such indemnification is against public policy as expressed in the
Act and is, therefore, unenforceable. In the event that a claim for
indemnification against such liabilities (other than the payment by the
registrant of expenses incurred or paid by a director, officer, or controlling
person of the registrant in the successful defense of any action suit, or
proceeding) is asserted by such director, officer, or controlling person in
connection with the securities being registered, the registrant will, unless in
the opinion of its counsel the matter has been settled by controlling precedent,
submit to a court of appropriate jurisdiction the question whether such
indemnification by it is against public policy as expressed in the Securities
Act of 1933 and will be governed by the final adjudication of such issue.





                                       30




                                   SIGNATURES

         Pursuant to the requirements of the Securities Act of 1933, the
Registrant certifies that it has reasonable grounds to believe that it meets all
of the requirements for filing on Form S-3 and has duly caused this Registration
Statement to be signed on its behalf by the undersigned, thereunto duly
authorized, in the City of Gaithersburg and State of Maryland on the 12 day of
April, 2002.

                                    IGEN INTERNATIONAL, INC.

                                    By: /s/ Samuel J. Wohlstadter
                                    -----------------------------
                                    Samuel J. Wohlstadter
                                    Chairman and Chief Executive Officer


                                POWER OF ATTORNEY

         Each person whose signature appears below hereby appoints each of
Samuel J. Wohlstadter, Richard J. Massey and George V. Migausky severally,
acting alone and without the other, his/her true and lawful attorney-in-fact
with the authority to execute in the name of each such person, any and all
amendments (including without limitation, post-effective amendments) to this
Registration Statement on Form S-3, to sign any and all additional registration
statements relating to the same offering of securities as this Registration
Statement that are filed pursuant to rule 462(b) of the Securities Act, and to
file such registration statements with the Securities and Exchange Commission,
together with any exhibits thereto and other documents therewith, necessary or
advisable to enable the Registrant to comply with the Securities Act, and any
rules, regulations and requirements of the Securities and Exchange Commission in
respect thereof, which amendments may make such other changes in the
Registration Statement as the aforesaid attorney-in-fact executing the same
deems appropriate.

         Pursuant to the requirements of the Securities Act of 1933, this
Registration Statement has been signed below by the following persons in the
capacities and on the dates indicated.



                                                                          
SIGNATURE                                TITLE                                  DATE

/s/ Samuel J. Wohlstadter                Chairman, Chief Executive Officer
-------------------------                (Principal Executive Officer);         April 12, 2002
Samuel J. Wohlstadter                    Director

                                         Vice President and Chief Financial     April 12, 2002
/s/ George V. Migausky                   Officer (Principal Financial and
------------------------                 Accounting Officer)
George V. Migausky

                                         President, Chief Operating Officer;    April 12, 2002
/s/ Richard J. Massey                    Director
------------------------
Richard J. Massey

/s/ Richard W. Cass
-------------------                      Director                               April 12, 2002
Richard W. Cass


/s/ Anthony Rees
----------------                         Director                               April 12, 2002
Anthony Rees

/s/ Robert R. Salsmans
----------------------                   Director                               April 12, 2002
Robert R. Salsmans


/s/ Joop Sistermans
-------------------                      Director                               April 12, 2002
Joop Sistermans






                                       31





                                  EXHIBIT INDEX

         Exhibit
         Number      Description

         4.7         Form of Common Stock Certificate (Previously filed
                     and incorporated by reference to Registration
                     Statement on Form 8-A of the Company filed with the
                     Securities and Exchange Commission on December 10,
                     1996).

         5.1         Opinion of Kirkpatrick & Lockhart LLP regarding legality.

         23.1        Consent of Kirkpatrick & Lockhart LLP (see Exhibit 5.1).

         23.2        Consent of Deloitte & Touche LLP.

         24.1        Power of Attorney (included on signature page).

         ---------------------------





                                       32