SECURITIES AND EXCHANGE COMMISSION
                              WASHINGTON, DC 20549

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


                                  SCHEDULE 13D


                   Under the Securities Exchange Act of 1934



                       Integrated Security Systems, Inc.
--------------------------------------------------------------------------------
                                (Name of Issuer)

                                  Common Stock
--------------------------------------------------------------------------------
                         (Title of Class of Securities)

                                   45812J101
--------------------------------------------------------------------------------
                                 (CUSIP Number)

                               Russell Cleveland
                        Renaissance Capital Group, Inc.
                  8080 N. Central Expressway, Suite 210, LB-59
                            Dallas, Texas 75206-1857
                                 (214) 891-8294
--------------------------------------------------------------------------------
                 (Name, Address and Telephone Number of Person
               Authorized to Receive Notices and Communications)

                                  May 17, 2001
            (Date of Event Which Requires Filing of This Statement)

If the filing person has previously  filed a statement on Schedule 13G to report
the  acquisition  which is the subject of this  Schedule 13D, and is filing this
schedule  because  of  Section  240.13d-1(e),  Section  240.13d-1(f)  or Section
240.13d-1(g), check the following box [ ].


                         (Continued on following pages)










CUSIP No. 45812J101                                          13D
---------------------------------------



   1     NAME OF REPORTING PERSON                   I.R.S. IDENTIFICATION NUMBER
         Renaissance Capital Growth & Income Fund III, Inc.           75-2533518
--------------------------------------------------------------------------------


   2     CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP         (a) [ ]
                                                                  (b) [x]

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


   3     SEC USE ONLY

   4     SOURCE OF FUNDS
                  WC
--------------------------------------------------------------------------------


   5     CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED
         PURSUANT TO ITEM 2(d) or 2(e)                                [ ]
--------------------------------------------------------------------------------


   6     CITIZENSHIP OR PLACE OF ORGANIZATION
                  Texas
--------------------------------------------------------------------------------


        NUMBER OF            7    SOLE VOTING POWER            21,194,758
         SHARES
      BENEFICIALLY
        OWNED BY
          EACH
        REPORTING
       PERSON WITH

                             8    SHARED VOTING POWER          None

                             9    SOLE DISPOSITIVE POWER       21,194,758

                            10    SHARED DISPOSITIVE POWER     None
--------------------------------------------------------------------------------


  11     AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
                  21,194,758 shares
--------------------------------------------------------------------------------


  12     CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES
         CERTAIN SHARES                                               [ ]
--------------------------------------------------------------------------------


  13     PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)
                  67.1%

  14     TYPE OF REPORTING PERSON
                  IV
--------------------------------------------------------------------------------











CUSIP No. 45812J101                                          13D
---------------------------------------



   1     NAME OF REPORTING PERSON                   I.R.S. IDENTIFICATION NUMBER
         Renaissance US Growth & Income Trust PLC                 None - Foreign
--------------------------------------------------------------------------------


   2     CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP         (a) [ ]
                                                                  (b) [x]

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


   3     SEC USE ONLY

   4     SOURCE OF FUNDS
                  WC
--------------------------------------------------------------------------------


   5     CHECK BOX IF DISCLOSURE OF LEGAL PROCEEDINGS IS REQUIRED
         PURSUANT TO ITEM 2(d) or 2(e)                            [  ]
--------------------------------------------------------------------------------


   6     CITIZENSHIP OR PLACE OF ORGANIZATION
                  England
--------------------------------------------------------------------------------


        NUMBER OF            7    SOLE VOTING POWER            20,358,446
         SHARES
      BENEFICIALLY
        OWNED BY
          EACH
        REPORTING
       PERSON WITH

                             8    SHARED VOTING POWER          None

                             9    SOLE DISPOSITIVE POWER       20,358,446

                            10    SHARED DISPOSITIVE POWER     None
--------------------------------------------------------------------------------


  11     AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
                  20,358,446 shares
--------------------------------------------------------------------------------


  12     CHECK BOX IF THE AGGREGATE AMOUNT IN ROW (11) EXCLUDES
         CERTAIN SHARES                                           [ ]
--------------------------------------------------------------------------------


  13     PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (11)
                  66.2%

  14     TYPE OF REPORTING PERSON
                  IV
--------------------------------------------------------------------------------











Item 1.           Security and Issuer.

         This  statement  relates  to the  Common  Stock  ("Common  Shares")  of
Integrated  Security  Systems,  Inc. (the  "Company").  The principal  executive
offices of the Company  are  located at 8200  Springwood  Drive,  Irving,  Texas
75063.

Item 2.       Identity and Background.

         (a) This Statement is filed by Renaissance Capital Growth & Income Fund
III, Inc.  ("Renaissance  III"),  and  Renaissance  US Growth & Income Trust PLC
("Renaissance  PLC";  Renaissance III and  Renaissance  PLC,  collectively,  the
"Reporting Persons").

         Certain information  concerning the directors and executive officers of
the  Reporting  Persons  is set  forth  on  Attachment  1  attached  hereto  and
incorporated herein by reference.

         (b) Renaissance III is a business  development  company regulated under
the Investment Company Act of 1940, as amended,  and organized under the laws of
the State of Texas, with its principal  business and principal office at 8080 N.
Central Expressway, Suite 210, LB 59, Dallas, Texas 75206-1857.

         Renaissance  PLC is an  investment  trust  organized  under the laws of
England and Wales.  Its address in the United States is c/o Renaissance  Capital
Group, Inc., Investment Manager,  8080 N. Central Expressway,  Suite 210, LB 59,
Dallas, Texas 75206-1857.

         The business  addresses of the directors and executive  officers of the
Reporting  Persons  are  set  forth  on  Attachment  1  to  this  Statement  and
incorporated herein by reference.

         (c)  Renaissance III and Renaissance PLC are engaged in the business of
investing principally in emerging or undervalued U.S. public companies.

         (d) Neither any of the Reporting  Persons nor, to the best knowledge of
such  persons,  any person  named in  Attachment 1 to this  Statement,  has been
convicted in a criminal  proceeding  in the past five years  (excluding  traffic
violations or similar misdemeanors).

         (e) Neither any of the Reporting  Persons nor, to the best knowledge of
such persons, any person named in Attachment 1 to this Statement, was during the
last five years a party to a civil  proceeding  of a judicial or  administrative
body of  competent  jurisdiction  as a result  of which  such  person  was or is
subject to a judgment,  decree or final order enjoining future violations of, or
prohibiting or mandating activities subject to, federal or state securities laws
or finding any violation with respect to such laws.

         (f) All persons named on Attachment 1 to this Statement are citizens of
the United States, except as otherwise indicated on such Attachment.



                                     Page 4





Item 3.      Source and Amount of Funds or Other Consideration.

             The total amount of funds  required by  Renaissance  III to acquire
the securities  reported in Item 5(a) was  $4,329,589.  The source of such funds
was capital of Renaissance III.

             The total amount of funds  required by  Renaissance  PLC to acquire
the securities  reported in Item 5(a) was  $4,163,463.  The source of such funds
was capital of Renaissance PLC.

Item 4.      Purpose of Transaction.

             The  Reporting  Persons each acquired  beneficial  ownership of the
Common Stock  reported in Item 5(a) both in the ordinary  course of business for
investment  purposes and upon exchange of  indebtedness  in connection  with the
financial  restructuring  of the Company.  The President and CEO of  Renaissance
Capital  Group,  Inc.,  the  investment  advisor  to  Renaissance  III  and  the
investment manager of Renaissance PLC, Russell Cleveland,  has been appointed to
the board of directors of the Company.

             The  Reporting   Persons  may   participate  in  discussions   with
management or third parties in which the Reporting  Person may suggest or take a
position  with respect to potential  changes in the  operations,  management  or
capital structure of such companies as a means of enhancing  shareholder  value.
Such  suggestions  or  positions  may relate to one or more of the  transactions
specified  in  clauses  (a)  through  (j) of Item 4 of the  Schedule  13D  form,
including,  without  limitation,  such  matters  as  disposing  of one  or  more
businesses,  selling the  Company,  merging  with  another  Company or acquiring
another company or business, changing operating or marketing strategies, changes
in management or marketing or restructuring the Company's capitalization.

              Each Reporting Person continues to assess the Company's  business,
financial  condition,  results of operations  and  prospects,  general  economic
conditions,  the  securities  markets  in  general  and those for the  Company's
securities in particular, other developments and other investment opportunities,
as well as the  Reporting  Person's  investment  objectives.  Depending  on such
assessments,  one or  both  of the  Reporting  Persons  may  acquire  additional
securities or may  determine to sell or otherwise  dispose of some or all of its
holdings of securities.

              Other than as described above, either of the Reporting Persons has
any  present  plans  or  proposals  which  relate  to or  would  result  in  any
transaction,  change or event  specified in clauses (a) through (j) of Item 4 of
the Schedule 13D.

Item 5.      Interest in Securities of the Issuer.

             (a) Renaissance III beneficially owns 21,194,758 Common Shares, and
Renaissance  PLC  beneficially  owns  20,358,446  Common  Shares.  The Reporting
Persons  beneficially  own  40,553,204  Common  Shares.  Based upon  information
contained in the Company's most recent public filing containing such information
filed  with  the   Securities  and  Exchange   Commission,   the  Common  Shares
beneficially  owned by Renaissance III,  Renaissance PLC and together  represent
approximately  67.1%, 66.2% and 80.6%,  respectively,  of the outstanding Common
Stock of the Company. Renaissance III and Renaissance PLC disclaim that they are
members of a group for purposes of Regulation 13D.


                                     Page 5





             The  Common  Shares  beneficially  owned  by  Renaissance  III  are
comprised  of 393,259  shares of Common  Stock;  814,299  shares of Common Stock
issuable upon the exercise of warrants;  187,500 shares of Common Stock issuable
upon the  conversion  of 7,500  shares of Series D  Preferred  Stock;  2,589,945
shares of Common Stock  issuable  upon  conversion  of 20,720 shares of Series F
Convertible  Preferred Stock ("Series F Preferred Stock"); and 17,209,755 shares
of  Common  Stock  issuable  upon  conversion  of  137,678  shares  of  Series G
Convertible Preferred Stock ("Series G Preferred Stock"). The board of directors
of Renaissance III exercises  voting and investment  control over the securities
of the Company owned by it.

             Renaissance  PLC is deemed the  beneficial  owner of Common  Shares
comprised  of 393,258  shares of Common  Stock;  808,617  shares of Common Stock
issuable upon the exercise of warrants;  187,500 shares of Common Stock issuable
upon the  conversion  of 7,500  shares of Series D  Preferred  Stock;  2,589,945
shares of Common Stock  issuable  upon  conversion  of 20,720 shares of Series F
Preferred Stock; and 16,379,126  shares of Common Stock issuable upon conversion
of  131,033  shares of Series G  Preferred  Stock.  The  board of  directors  of
Renaissance PLC exercises  voting and investment  control over the securities of
the Company owned by it.

             (b)  Holders of Series D Preferred  Stock are  entitled to one vote
for each share of Common Stock into which such share of Series D Preferred Stock
could  then be  converted.  Presently,  the  holder  of each  share of  Series D
Preferred Stock is entitled to 25 votes. Holders of Series F Preferred Stock are
entitled to vote with the holders of Common Stock, the Series D Preferred Stock,
the Series E Preferred Stock, and the Series G Preferred Stock as a single class
on all  matters  on which  stockholders  are  entitled  to vote,  including  the
election of directors,  except as otherwise required by law. Holders of Series F
Preferred  Stock  are also  entitled  to vote  with any  other  class of  equity
securities which may vote with the holders of the Common Stock as a single class
with respect to any matter.  Holders of Series F Preferred Stock are entitled to
a number of votes per share of Series F  Preferred  Stock equal to the number of
shares of Common  Stock into which the  shares of Series F  Preferred  Stock are
convertible on the record date of the determination of stockholders  entitled to
receive  notice of and to vote on such  matter.  In  addition,  the  consent  of
holders of 80% of the Series F Preferred Stock and the Series G Preferred Stock,
voting together as a single class, will be required to (a) authorize,  create or
increase the  authorized  amount of any class of senior  stock or parity  stock,
other than Preferred Stock of the same class or securities to evidence bank debt
or asset  securitizations  or (b) authorize a merger,  consolidation  or sale of
assets, other than in the ordinary course of business, of the Company, including
the capital stock of the Company's  subsidiaries.  The consent of holders of 80%
of the Series F Preferred Stock,  voting as a single class,  will be required to
approve any action to amend the Company's certificate of incorporation or bylaws
that would  materially and adversely affect the rights of the Series F Preferred
Stock.

             Holders of Series G  Preferred  Stock will be entitled to vote with
the  holders  of Common  Stock,  the  Series D  Preferred  Stock,  the  Series E
Preferred  Stock,  and the  Series F  Preferred  Stock as a single  class on all
matters on which  stockholders  are entitled to vote,  including the election of
directors,  except as otherwise  required by law.  Holders of Series G Preferred
Stock are also entitled to vote with any other class of equity  securities which
may vote with the holders of the Common  Stock as a single class with respect to
any  matter.  Holders of Series G  Preferred  Stock are  entitled to a number of
votes per share of Series G  Preferred  Stock  equal to the  number of shares of
Common Stock into which the shares of Series G Preferred  Stock are  convertible
on the record  date of the  determination  of  stockholders  entitled to receive
notice of and to vote on such matter. In addition, the consent of holders of 80%


                                     Page 6





of  the  Series G  Preferred  Stock and  the  Series F Preferred  Stock,  voting
together  as  a  single  class,  will be  required  (a) to  authorize, create or
increase  the  authorized  amount  of any class of senior stock or parity stock,
other than Preferred Stock of the same class or securities to evidence bank debt
or  securitizations or (b) authorize a merger, consolidation or sale of  assets,
other than in the ordinary  course  of  business,  of the Company, including the
capital  stock of the Company's subsidiaries.  The consent of holders of 80% of
the Series G  Preferred  Stock,  voting as a single  class,  will be required to
approve any  action  to amend  the  Company's  certificate  of  incorporation or
bylaws  that would  materially and  adversely affect the  rights of the Series G
Preferred Stock.

             In  addition  to their right to vote with the holders of the Common
Stock on the election of directors, the Reporting Persons, as the holders of the
Series G Preferred Stock and the holders of the Series F Preferred Stock, voting
together as a single class,  are entitled to elect two  additional  directors to
the Company's board of directors.

              Each of the  Reporting  Persons has or will have upon the exercise
of the  warrants  issued to it by the Company the sole power to vote and dispose
of all of the Common  Shares that it  beneficially  owns.  None of the Reporting
Persons shares voting or  disposition  power with any person with respect to the
Common Shares.

             (c) No transaction in the Common Shares was effected by a Reporting
Person  during the past 60 days,  other than the  issuance on May 17,  2001,  in
connection with a financial  restructuring of the Company, to Renaissance III of
20,720  shares  of  Series F  Preferred  Stock  and  137,678  shares of Series G
Preferred Stock and the issuance to Renaissance PLC of 20,720 shares of Series F
Preferred  Stock and 131,033  shares of Series G Preferred  Stock.  All of these
shares were issued in exchange  for  approximately  $7.5  million of  promissory
notes and convertible  debentures  owned by Renaissance III and Renaissance PLC,
including accrued interest, in connection with a financial  restructuring of the
Company.

             (d) No person  other than the  Reporting  Persons  has the right to
receive or the power to direct the receipt of  dividends  from,  or the proceeds
from the sale of, the Common Shares beneficially owned by the Reporting Persons.

             (e)  Not applicable.

Item 6.      Contracts,  Arrangements,  Understandings  or  Relationships   With
             Respect to Securities of the Issuer.

             Not applicable.

Item 7.      Material to Be Filed as Exhibits.

                  Exhibit 1    Joint Filing Agreement Pursuant to Rule 13d-1(k)



                                     Page 7





                                   SIGNATURES

         After reasonable inquiry and to the best of their individual  knowledge
and belief, the signatories below certify that the information set forth in this
statement is true, complete, and correct as of this 23rd day of May, 2001.

         The persons whose signatures  appear below agree that this statement on
Schedule 13D is filed on behalf of each of them.



                                  RENAISSANCE CAPITAL GROWTH &
                                  INCOME FUND III, INC.


                                  By:     /s/
                                  Name:   Russell Cleveland
                                  Title:  President and Chief Executive Officer

                                  RENAISSANCE US GROWTH & INCOME
                                  TRUST PLC


                                  By:     /s/
                                  Name:   Russell Cleveland
                                  Title:  Director



                                     Page 8





                                                   ATTACHMENT 1

         The name,  business  address and principal  occupation of the directors
and executive officers of Renaissance III are as follows:


DIRECTORS

                                                                 Principal
Name                      Business Address                       Occupation

Edward O. Boshell, Jr.    c/o Renaissance Capital Group, Inc.    Director
                          8080 North Central Expressway
                          Suite 210, LB 59
                          Dallas, Texas  75206-1857
Russell Cleveland         c/o Renaissance Capital Group, Inc.    Director
                          8080 North Central Expressway
                          Suite 210, LB 59
                          Dallas, Texas  75206-1857
Peter Collins             c/o Renaissance Capital Group, Inc.    Director
                          8080 North Central Expressway
                          Suite 210, LB 59
                          Dallas, Texas  75206-1857
Ernest C. Hill            c/o Renaissance Capital Group, Inc.    Director
                          8080 North Central Expressway
                          Suite 210, LB 59
                          Dallas, Texas  75206-1857

OFFICERS

Russell Cleveland         c/o Renaissance Capital Group, Inc.    President and
                          8080 North Central Expressway          Chief Executive
                          Suite 210, LB 59                       Officer
                          Dallas, Texas  75206-1857
John A. Schmit            c/o Renaissance Capital Group, Inc.    Vice President
                          8080 North Central Expressway
                          Suite 210, LB 59
                          Dallas, Texas  75206-1857
Robert C. Pearson         c/o Renaissance Capital Group, Inc.     Vice President
                          8080 North Central Expressway
                          Suite 210, LB 59
                          Dallas, Texas  75206-1857
Barbara A. Butschek       c/o Renaissance Capital Group, Inc.    Secretary and
                          8080 North Central Expressway          Treasurer
                          Suite 210, LB 59
                          Dallas, Texas  75206-1857



                                     Page 9





         The name,  business  address and principal  occupation of the directors
and executive officers of Renaissance PLC are as follows:


DIRECTORS

                                                                    Principal
Name                              Business Address                  Occupation

Michael B. Cannan                 c/o Sinclair Henderson Limited    Director
                                  23 Cathedral Yard
                                  Exeter EX11HB
Russell Cleveland                 c/o Sinclair Henderson Limited    Director
                                  23 Cathedral Yard
                                  Exeter EX11HB
Ernest J. Fenton                  c/o Sinclair Henderson Limited    Director
                                  23 Cathedral Yard
                                  Exeter EX11HB
Lord Mark Fitzalan Howard OBE     c/o Sinclair Henderson Limited    Director
                                  23 Cathedral Yard
                                  Exeter EX11HB
C.A. Rundell, Jr.                 c/o Sinclair Henderson Limited    Director
                                  23 Cathedral Yard
                                  Exeter EX11HB
William W. Vanderfelt             c/o Sinclair Henderson Limited    Director
                                  23 Cathedral Yard
                                  Exeter EX11HB

OFFICERS

None



                                    Page 10




                                                                       EXHIBIT 1

                JOINT FILING AGREEMENT PURSUANT TO RULE 13d-1(k)

         The undersigned  acknowledge and agree that the foregoing  statement on
Schedule  13D is  filed  on  behalf  of each of the  undersigned  and  that  all
subsequent amendments to this statement on Schedule 13D shall be filed on behalf
of each of the  undersigned  without the  necessity of filing  additional  joint
filing  agreements.  The undersigned  acknowledge that each shall be responsible
for the timely filing of such amendments,  and for the completeness and accuracy
of the information concerning it contained therein, but shall not be responsible
for the  completeness  and accuracy of the  information  concerning  the others,
except to the extent it knows or has reason to believe that such  information is
inaccurate.  This  Joint  Filing  Agreement  may be  executed  in any  number of
counterparts  and all of such  counterparts  taken together shall constitute one
and the same instrument.


                                  RENAISSANCE CAPITAL GROWTH &
                                  INCOME FUND III, INC.


                                  By:     /s/
                                  Name:   Russell Cleveland
                                  Title:  President and Chief Executive Officer

                                  RENAISSANCE US GROWTH & INCOME
                                  TRUST PLC


                                  By:     /s/
                                  Name:   Russell Cleveland
                                  Title:  Director




                                    Page 11