As filed with the Securities and Exchange Commission on July 8, 2005        
                                                                No. 333 - 122687
================================================================================

                                                                           

                UNITED STATES SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549


                          PRE-EFFECTIVE AMENDMENT NO. 2
                                       TO
                                    FORM S-3



             REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933

                        NATURAL GAS SERVICES GROUP, INC.
             (Exact name of registrant as specified in its charter)

             Colorado                                    75-2811855             
  (State or other jurisdiction of                     (I.R.S. Employer          
   incorporation or organization)                  Identification Number)       
                                                                                
                                                      Stephen C. Taylor         
    2911 South County Road 1260                  2911 South County Road 1260    
       Midland, Texas 79706                         Midland, Texas 79706        
          (432) 563-3974                               (432) 563-3974           
   (Address, including zip code,             (Name, address, including zip code,
 and telephone number, including,                code and telephone number,     
area code of registrant's principal             including, area code of agent   
        executive offices)                              for service)            
                                             
                                   Copies to:
                                 David A. Thayer
                               Jackson Kelly PLLC
                          1099 18th Street, Suite 2150
                                Denver, CO 80202
                            Telephone: (303) 390-0003

     Approximate date of commencement of proposed sale to the public: As soon as
practicable after the effective date of this Registration Statement.

     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

============================== ================== ================== ===================== ====================
                                                       Proposed           Proposed
                                    Amount              Maximum             Maximum
Title of Each Class of              to be           Offering Price        Aggregate             Amount of
Securities to be Registered      Registered (1)      Per Share (2)    Offering Price (2)     Registration Fee
------------------------------ ------------------ ------------------ --------------------- --------------------
                                                                                 
Common Stock, $.01 par value 
per share                          701,171              $10.35           $7,257,120             $855 (3)
============================== ================== ================== ===================== ====================



(1)  Pursuant  to Rule  416 of the  Securities  Act of 1933,  this  registration
     statement shall cover such indeterminate number of additional shares of the
     Registrant's  Common Stock as may be issued as a result of stock dividends,
     stock  splits,  recapitalizations,  or  similar  transactions  prior to the
     termination of this registration statement.

(2)  Estimated  solely  for the  purpose of  calculating  the  registration  fee
     pursuant to Rule 457(c) under the Securities Act of 1933, as amended, based
     upon the closing price of the Registrant's Common Stock on May 18, 2005, as
     quoted on the American Stock Exchange.


(3)  Previously paid.



     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.

                                                                         



         The  information in this prospectus is not complete and may be changed.
The  selling  shareholders  may not sell these  securities  in  reliance on this
prospectus  until the  registration  statement  filed  with the  Securities  and
Exchange  Commission,  of which this  prospectus is a part,  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.



PROSPECTUS                SUBJECT TO COMPLETION, DATED
                                  July 8, 2005



                                 701,171 SHARES


                        NATURAL GAS SERVICES GROUP, INC.

                                  Common Stock

         This prospectus  relates to 701,171 shares of our common stock that may
be offered for sale or otherwise transferred from time to time by certain of our
shareholders.  See "Selling  Shareholders" on page 16. Of these shares,  118,968
shares are  outstanding as of the date of this  prospectus,  while the remaining
582,203  shares will be issuable  upon the  exercise of  warrants.  Warrants for
616,175  of the  shares  were  issued by us in early  2001 when we  completed  a
private  placement of units  consisting  of the  warrants  and 10%  subordinated
notes.  The  remaining  warrants  for 84,996 were issued in March 2001 and April
2002 to several of our affiliates in consideration for their personal guarantees
of  our  corporate  debt.  See  "SELLING  SHAREHOLDERS"  on  page  16  for  more
information concerning the issuance of the warrants.


         Our common stock is quoted on the  American  Stock  Exchange  under the
symbol  "NGS".  On July 5, 2005,  the closing sale price of our common stock was
$11.75 per share.


         Our principal  executive office is located at 2911 S. County Road 1260,
Midland, Texas 79706 and the telephone number is (432) 563-3974.

         The  selling  shareholders  may offer  these  shares  from time to time
through public or private  transactions at market prices  prevailing at the time
of sale, at prices  related to prevailing  market prices or at other  negotiated
prices.  The  selling  shareholders  may sell  none,  some or all of the  shares
offered  by this  prospectus.  We cannot  predict  when or in what  amounts  the
selling shareholders may sell any of the shares offered by this prospectus.  The
selling  shareholders will generally be responsible for their legal fees and for
any  commissions  or discounts due to brokers or dealers.  We will pay the other
offering  expenses.  We will not  receive any of the  proceeds  from the sale of
shares by selling shareholders under this prospectus. See "Plan of Distribution"
on page 16.


         PROSPECTIVE  PURCHASERS OF THE COMMON STOCK SHOULD  CONSIDER  CAREFULLY
THE MATTERS SET FORTH UNDER "RISK FACTORS" BEGINNING ON PAGE 4.


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


                  The date of this Prospectus is July __, 2005.





                    WHERE YOU CAN FIND ADDITIONAL INFORMATION

         We file annual,  quarterly and special  reports,  proxy  statements and
other information with the Securities and Exchange  Commission (or SEC). You may
read and copy  materials  that we have filed with the  Securities  and  Exchange
Commission at the following  Securities and Exchange Commission public reference
room:

                             450 Fifth Street, N.W.
                             Washington, D.C. 20549

         Please call the  Securities and Exchange  Commission at  1-800-SEC-0330
for further information on the public reference room.

         The shares of common stock of Natural Gas Services  Group are traded on
the American Stock Exchange under the symbol "NGS".

         Our  Securities and Exchange  Commission  filings are also available to
the public on the  Securities  and  Exchange  Commission's  internet  website at
http://www.sec.gov.  In addition,  the filings  Natural Gas Services Group makes
with the Securities and Exchange  Commission are also available to the public on
Natural Gas Services Group's website, www.ngsgi.com.  Information on our website
is not incorporated into this prospectus and is not part of this prospectus.

         We  have  filed  with  the   Securities   and  Exchange   Commission  a
registration  statement  on  Form  S-3  covering  the  shares  offered  by  this
prospectus.  The  registration  statement,  including the attached  exhibits and
schedules,  contains  additional  relevant  information  about us and our common
stock, and you should refer to the applicable exhibit or schedule for a complete
description of any statement  referring to any contract or other  document.  The
rules and regulations of the Securities and Exchange Commission allow us to omit
certain information included in the registration statement from this prospectus.


                     INCORPORATION OF DOCUMENTS BY REFERENCE

         The SEC allows us to  "incorporate  by reference" some of the documents
we file with it. This means that we can disclose important information to you by
referring you to those documents.  The information  incorporated by reference is
considered to be part of this  prospectus,  and  information  that we file later
with the SEC will  automatically  update and  supersede  this  information.  The
documents we incorporate by reference are:

         o        Our  Quarterly  Report on Form  10-QSB for the  quarter  ended
                  March 31, 2005, and amended on July 8, 2005;

         o        Our Annual  Report on Form 10-KSB for the year ended  December
                  31, 2004, and amended on May 4, 2005 and July 8, 2005;

         o        Our Current  Reports on Form 8-K filed with the Securities and
                  Exchange  Commission  on January 7, 2005,  January  13,  2005,
                  January 26, 2005,  February 24, 2005,  March 18, 2005, and May
                  13, 2005;



                                       2


         o        The description of our common stock contained in Items 1 and 2
                  of our Registration  Statement on Form 8-A filed under Section
                  12 of the Securities Exchange Act of 1934 (or Exchange Act) on
                  July 17, 2002; and

         o        All documents we file pursuant to Sections 13(a), 13(c), 14 or
                  15(d) of the  Exchange  Act after the date of this  prospectus
                  and prior to the  termination  of the  offering  of the shares
                  offered hereby.

         We will provide at no cost to each  person,  including  any  beneficial
owner, to whom this  prospectus is delivered,  on the written or oral request of
such person,  a copy of any or all of the documents we incorporate by reference,
other than exhibits to such documents  (unless those  exhibits are  specifically
incorporated by reference into the documents that this prospectus incorporates).
Requests  should be directed to Natural Gas  Services  Group,  Inc.,  2911 South
County Road 1260,  Midland,  Texas 79706,  (432) 563-3974,  Attention:  Investor
Relations.

         We have  not  authorized  anyone  to give any  information  or make any
representation  about  us  that is  different  from,  or in  addition  to,  that
contained  in  this  prospectus  or  in  any  of  the  materials  that  we  have
incorporated by reference into this document. Therefore, if anyone does give you
information  of  this  sort,  you  should  not  rely  on  it.  If  you  are in a
jurisdiction  where offers to sell, or solicitations of offers to purchase,  the
shares of common stock  offered by this  document is  unlawful,  or if you are a
person to whom it is unlawful  to direct  these  types of  activities,  then the
offer  presented in this document does not extend to you. You should assume that
the  information  appearing in this  prospectus,  as well as the  information we
previously filed with the SEC and incorporated by reference, is accurate only as
of the date of the documents containing the information.

                     ABOUT NATURAL GAS SERVICES GROUP, INC.

         We provide  equipment and services to the natural gas and oil industry.
We manufacture,  fabricate,  sell and lease natural gas compressors that enhance
the  production  of oil and gas wells and we provide  maintenance  services  for
those  compressors.  We define a natural gas  compressor as a mechanical  device
with one basic goal - to deliver gas at a pressure  higher than that  originally
existing. It may be powered by a natural gas burning engine or an electric motor
to  accommodate  different  applications.   Gas  compression  is  undertaken  to
transport and distribute  natural gas to pipelines.  Pipeline pressures vary and
with the  addition  of new  wells  to the  pipeline,  the  need for  compression
increases.  We also manufacture and sell flare tips and ignition systems for oil
and gas plant and  production  facilities.  We define a flare tip as a burner on
the upper end of a flare stack that is designed to combust waste gases to assure
a clean  environment.  An ignition  system is a pilot light or a spark generator
that assures continuous  ignition of the waste gases going through the burner in
the flare tip.

         We primarily  lease and sell natural gas  compressors.  As of March 31,
2005, we had 661 natural gas compressors under lease to third parties.

         We also fabricate natural gas compressors for our customers,  designing
compressors to meet unique specifications dictated by well pressures, production
characteristics and particular applications for which compression is sought.

         We have  established an exchange and rebuild program to attempt to help
minimize  costs and maximize  revenue for our customers.  Under the program,  we
work  with  maintenance  and  operating  personnel  of a  customer  to  identify
equipment for exchange.  When we receive a compressor for exchange  because of a
maintenance problem, we deliver to our customer a replacement compressor at full
price. We then rebuild the exchange compressor and credit our customer an amount
based on the  value of the  rebuilt  compressor.  We also  offer a  retrofitting
service by repackaging a customer's  compressor with a compressor that meets our
customer's changed conditions.



                                       3


         We design,  manufacture,  install and service  flare stacks and related
ignition and control  devices for onshore and offshore  burning of gas compounds
such as hydrogen sulfide,  carbon dioxide,  natural gas and liquefied  petroleum
gases.

         We have  manufacturing and fabrication  facilities located in Lewiston,
Michigan,  Tulsa,  Oklahoma,  and  Midland,  Texas,  where  we  manufacture  and
fabricate natural gas compressors.  We design and manufacture  natural gas flare
systems,  components and ignition systems in our facility in Midland, Texas, for
use in oilfield,  refinery and petrochemical plant  applications.  On January 3,
2005, we acquired  Screw  Compression  Systems,  Inc., a Tulsa,  Oklahoma  based
manufacturer of natural gas compressors.

         We currently  provide our  products and services to a customer  base of
oil  and  gas  exploration  and  production  companies  operating  primarily  in
Colorado, Kansas, Louisiana, Michigan, New Mexico, Oklahoma, Texas and Wyoming.

         We  maintain  our  principal  office at 2911  South  County  Road 1260,
Midland, Texas 79706 and our telephone number is (432) 563-3974.


                                  RISK FACTORS

         To inform investors of our future plans and objectives, this prospectus
(and other  reports and  statements  issued by us and our officers  from time to
time) contain certain statements concerning our future performance,  intentions,
objectives,   plans  and   expectations   that  are  or  may  be  deemed  to  be
"forward-looking  statements." See "Forward Looking  Statements" on page 13. Our
ability to do this has been fostered by the Private Securities Litigation Reform
Act of 1995,  which provides a "safe harbor" for  forward-looking  statements to
encourage  companies  to  provide  prospective  information  so  long  as  those
statements  are  accompanied  by meaningful  cautionary  statements  identifying
important  factors that could cause  actual  results to differ  materially  from
those discussed in the statement.

         You  should  carefully  consider  the  following  risks.  The risks and
uncertainties  described below are not the only ones facing us. Additional risks
and  uncertainties  that are not presently known to us or that we currently deem
immaterial may also impair our business.

         If any of the events  described in the following  risks actually occur,
our business,  financial condition and results of operations could be materially
adversely  affected.  In such case, the trading prices of our common stock could
decline and you could lose all or part of your investment.

Our  current  debt is large and may  negatively  impact our  current  and future
financial stability.

         As of March 31, 2005, we had an aggregate of approximately  $24,400,000
of  outstanding  indebtedness,  not  including  accounts  payable,  and  accrued
expenses  of   approximately   $5,429,000.   As  a  result  of  our  significant
indebtedness,  we might not have the ability to incur any substantial additional
indebtedness. The level of our indebtedness could have several important effects
on our future operations, including:

         o        our  ability  to  obtain  additional   financing  for  working
                  capital, acquisitions, capital expenditures and other purposes
                  may be limited;



                                       4


         o        a significant  portion of our cash flow from operations may be
                  dedicated  to the  payment of  principal  and  interest on our
                  debt, thereby reducing funds available for other purposes; and

         o        our  significant  leverage  could make us more  vulnerable  to
                  economic downturns.

         If we are unable to service our debt,  we will likely be forced to take
remedial steps that are contrary to our business plan.

         As  of  March  31,  2005,  principal  payments  for  our  debt  service
requirements on a monthly, quarterly and annual basis were $449,000,  $1,350,000
and $5,399,000, respectively. It is possible that our business will not generate
sufficient cash flow from operations to meet our debt service  requirements  and
the payment of principal when due. If this were to occur, we may be forced to:

         o        sell assets at disadvantageous prices;

         o        obtain additional financing; or

         o        refinance all or a portion of our  indebtedness  on terms that
                  may be very unfavorable to us.

Our current bank loan contains  covenants that limit our operating and financial
flexibility and, if breached, could expose us to severe remedial provisions.

         Under the terms of our bank loan, we must:

         o        at the end of each month, have a current ratio of at least 1.4
                  to 1.0;

         o        at the end of each month,  have a  consolidated  tangible  net
                  worth of at least $14,500,000;

         o        at the end of each quarter,  have a ratio of (a)  consolidated
                  cash flow, to (b) consolidated  fixed charges of at least 1.25
                  to 1.0; and

         o        at the  end  of  each  month,  not  permit  our  ratio  of (a)
                  consolidated  debt, to (b) consolidated  tangible net worth to
                  exceed 2.7 to 1.0.

         In addition to  customary  affirmative  covenants,  the loan  agreement
contains various restrictive covenants and compliance requirements.  Among these
restrictions are limitations on our ability to:

         o        dispose of assets;

         o        incur additional indebtedness;

         o        create liens on our assets;

         o        repurchase,  redeem  or  retire  our  capital  stock  or other
                  securities;



                                       5


         o        merge or consolidate,  or transfer all or substantially all of
                  our assets and the assets of our subsidiaries;

         o        engage  in  specified   transactions   with  subsidiaries  and
                  affiliates;

         o        materially amend or modify our existing compressor leases;

         o        declare or pay dividends on our capital stock; and

         o        make any  significant or  substantial  change in the nature of
                  our  business  as being  conducted  as of the date of the loan
                  agreement.

         Our ability to meet the financial  ratios and tests under our bank loan
can be affected by events beyond our control,  and we may not be able to satisfy
those  ratios  and  tests.  A  breach  under  either  could  permit  the bank to
accelerate  the  debt so that it is  immediately  due and  payable.  No  further
borrowings  would be available under the credit  facility.  If we were unable to
repay the debt, the bank could proceed against our assets.

Approximately 69% of our compressor leases are leased for terms of six months or
less and, if terminated,  would adversely  impact our revenue and our ability to
recover our initial equipment costs.

         Approximately  69% of our compressor  leases are for terms of up to six
months.  There is a possibility that these leases could be terminated by lessees
within short  periods of time and that we may not be able to recover the cost of
a compressor for which a lease is terminated.

We must integrate the operations of acquired businesses.

         On January 3, 2005, we completed our  acquisition of Screw  Compression
Systems, Inc. ("SCS"). In connection with the acquisition, we nearly doubled our
long term debt and issued  609,576 of our shares of common  stock.  Our  success
will depend,  in part,  on our ability to integrate  the  operations  of SCS and
other  businesses  we  acquire in the  future,  including  centralizing  certain
functions to achieve cost savings,  pursuing programs and processes that promote
cooperation and the sharing of opportunities and resources, developing sales and
marketing  programs,  and retaining  acquired  customers.  We may not be able to
oversee the combined entity  efficiently or to implement  effectively our growth
and  operating  strategies.  To the extent that we  successfully  implement  our
acquisition  strategy,  our resulting growth will place  significant  additional
demands  on  our  management  and  infrastructure.   Our  failure  to  implement
successfully  our strategies or operate  effectively  the combined  entity could
have a material adverse effect on our business, financial condition, and results
of operations.  These effects could include lower revenue; higher cost of sales;
increased selling, general, and administrative expenses; and reduced margins.

The  anticipated  revenue  from the  affiliate  of Dominion  Michigan  cannot be
guaranteed.

         In connection with our acquisition of the compression-related assets of
Dominion Michigan,  an affiliate of Dominion Michigan committed until March 2006
to purchase  compressors  from us or enter into five year leases of  compressors



                                       6


with us totaling  five-thousand  horsepower.  If, for any reason,  the affiliate
does not fulfill this obligation to any material  extent,  our cash flow will be
significantly reduced and we may not be able to pay the principal or interest on
our debt as it becomes due.

We rely on two customers  for a significant  amount of our business and the loss
of these customers could  adversely  affect our operating  results and lower the
price of our common stock.

         Our business is dependent  not only on securing new  customers but also
on maintaining current customers. During the years ended December 2004 and 2003,
Dominion Exploration accounted for approximately 21% and 28% of our consolidated
revenue,  respectively.  For the three months  ended March  31,2005 our customer
XTO, obtained from the acquisition of SCS, represented 39% of total consolidated
revenue.  The loss of these two customers  could cause our operating  results to
fall  below  market  analysts'  expectations  and lower the price of our  common
stock.

We are dependent on a few suppliers for some of our  compressor  components  and
the loss of one of these suppliers could cause a delay in the  manufacturing  of
our compressors and reduce our revenue.

         We currently obtain approximately 20% of our compressor components from
three  suppliers.  We  order  from  these  suppliers  as  needed  and we have no
long-term  contracts with either  supplier.  If either of these suppliers should
curtail its operations or be unable to meet our needs, we would encounter delays
in supplying our customers with compressors  until an alternative  supplier,  if
any, could be found. Such delays in our  manufacturing  process could reduce our
revenue and negatively impact our relationships with customers.

Decreased oil and gas industry  expenditure  levels would  adversely  affect our
revenue.

         Our revenue is derived from  expenditures  in the oil and gas industry,
which in turn, are based on budgets to explore for,  develop and produce oil and
natural  gas. If these  expenditures  decline,  our  revenue  will  suffer.  The
industry's willingness to explore,  develop and produce depends largely upon the
prevailing view of future oil and gas prices. Many factors affect the supply and
demand for oil and gas and, therefore, influence product prices including:

         o        the level of oil and gas production;

         o        the levels of oil and gas inventories;

         o        the expected cost of developing new reserves;

         o        the cost of producing oil and gas;

         o        the level of drilling activity;

         o        inclement weather;

         o        worldwide economic activity;

         o        regulatory  and other  federal and state  requirements  in the
                  United States;



                                       7


         o        the  ability  of  the  Organization  of  Petroleum   Exporting
                  Countries to set and maintain production levels and prices for
                  oil;

         o        terrorist activities in the United States and elsewhere;

         o        the cost of developing alternate energy sources;

         o        environmental regulation; and

         o        tax policies.

         If  the  demand  for  oil  and  gas  decreases,  then  demand  for  our
compressors likely will decrease.

The intense  competition in our industry  could result in reduced  profitability
and loss of market share for us.

         We sell or lease our  products  and sell our  services  in  competitive
markets.  In most of our  business  segments,  we  compete  with the oil and gas
industry's  largest  equipment  and  service  providers  who have  greater  name
recognition  than  we  do.  These  companies  also  have  substantially  greater
financial  resources,  larger  operations  and greater  budgets  for  marketing,
research  and  development  than we do.  They may be better  able to  compete in
making  equipment  available  quickly  and more  efficiently,  meeting  delivery
schedules or reducing  prices.  As a result,  we could lose customers and market
share to those  competitors.  These companies may also be better positioned than
us successfully to endure downturns in the oil and gas industry.

         Our operations may be adversely affected if our current  competitors or
new market  entrants  introduce  new  products or services  with better  prices,
features, performance or other competitive characteristics than our products and
services.  Competitive pressures or other factors also may result in significant
price competition that could harm our revenue and our business.

We might be unable to employ adequate  technical  personnel,  which could hamper
our plans for expansion or increase our costs.

         Many of the compressors  that we sell or lease are technically  complex
and often must perform in harsh conditions.  We believe that our success depends
upon our ability to employ and retain a sufficient number of technical personnel
who have the ability to design, utilize, enhance and maintain these compressors.
Our ability to expand our operations  depends in part on our ability to increase
our skilled  labor force.  The demand for skilled  workers is high and supply is
limited. A significant  increase in the wages paid by competing  employers could
result in a reduction of our skilled  labor  force,  or cause an increase in the
wage rates that we must pay, or both.  If either of these  events were to occur,
our cost structure could increase and our operations and growth  potential could
be impaired.


If we do not develop, produce and commercialize new competitive technologies and
products, our revenue may decline.

         The markets for natural gas  compressor  products  and services and for
flare  systems,  ignition  systems  and  components  for  plant  and  production
facilities  are  characterized  by continual  technological  developments.  As a
result,  substantial  improvements in the scope and quality of product  function
and  performance  can occur over a short  period of time.  If we are not able to
develop  commercially  competitive  products  in a timely  manner in response to
changes in technology, our business and revenue may be adversely affected.



                                       8


         We  may  encounter   financial   constraints   or  technical  or  other
difficulties  that could delay  introduction of new products and services in the
future.  Our  competitors  may introduce new products before we do and achieve a
competitive advantage.

         Additionally,  the time and expense invested in product development may
not result in commercial applications that provide revenue. We could be required
to write  off our  entire  investment  in a new  product  that  does  not  reach
commercial  viability.  Moreover,  we may experience  operating losses after new
products are  introduced  and  commercialized  because of high  start-up  costs,
unexpected manufacturing costs or problems, or lack of demand.

We are  subject  to  extensive  environmental  laws and  regulations  that could
require us to take  costly  compliance  actions  that  could harm our  financial
condition.

         Our manufacturing and maintenance operations are significantly affected
by stringent and complex federal, state and local laws and regulations governing
the  discharge of  substances  into the  environment  or  otherwise  relating to
environmental  protection. In these operations, we generate and manage hazardous
wastes such as solvents,  thinner,  waste paint, waste oil, washdown wastes, and
sandblast material.  We attempt to use generally accepted operating and disposal
practices and, with respect to acquisitions, will attempt to identify and assess
whether there is any environmental risk before completing an acquisition.  Based
on the nature of the industry,  however,  hydrocarbons  or other wastes may have
been disposed of or released on or under properties  owned,  leased, or operated
by us or on or under  other  locations  where  such  wastes  have been taken for
disposal.  The  wastes on these  properties  may be  subject to federal or state
environmental laws that could require us to remove the wastes or remediate sites
where they have been  released.  We could be exposed to  liability  for  cleanup
costs,  natural  resource  and other  damages as a result of our  conduct or the
conduct of, or  conditions  caused by, prior  operators or other third  parties.
Environmental laws and regulations have changed in the past, and they are likely
to change in the future.  If existing  regulatory  requirements  or  enforcement
policies change,  we may be required to make significant  unanticipated  capital
and operating expenditures.

Any failure by us to comply with applicable  environmental  laws and regulations
may result in governmental  authorities taking actions against our business that
could harm our operations and financial condition, including the:

         o        issuance of administrative, civil and criminal penalties;

         o        denial or revocation of permits or other authorizations;

         o        reduction or cessation in operations; and

         o        performance   of  site   investigatory,   remedial   or  other
                  corrective actions.


         We could be subject to substantial liability claims that could harm our
financial condition.

         Our products are used in hazardous drilling and production applications
where an accident or a failure of a product can cause personal  injury,  loss of
life,  damage to  property,  equipment  or the  environment,  or  suspension  of
operations.



                                       9


         While we maintain insurance coverage, we face the following risks under
our insurance coverage:

         o        we may  not  be  able  to  continue  to  obtain  insurance  on
                  commercially reasonable terms;

         o        we may be faced  with  types of  liabilities  that will not be
                  covered by our  insurance,  such as damages  from  significant
                  product liabilities and from environmental contamination;

         o        the  dollar  amount of any  liabilities  may exceed our policy
                  limits; and

         o        we do not maintain  coverage  against the risk of interruption
                  of our business.

         Any claims  made under our policy  will  likely  cause our  premiums to
increase.  Any future  damages  caused by our products or services  that are not
covered  by  insurance,  are in  excess  of  policy  limits  or are  subject  to
substantial  deductibles,  would reduce our earnings and our cash  available for
operations.

Liability to customers under  warranties may materially and adversely affect our
earnings.

         We provide  warranties as to the proper  operation and  conformance  to
specifications  of the  equipment we  manufacture.  Our equipment is complex and
often  deployed  in harsh  environments.  Failure of this  equipment  to operate
properly  or  to  meet  specifications  may  increase  our  costs  by  requiring
additional  engineering  resources  and  services,   replacement  of  parts  and
equipment or monetary  reimbursement to a customer. We have in the past received
warranty claims and we expect to continue to receive them in the future.  To the
extent that we incur substantial  warranty claims in any period, our reputation,
our ability to obtain future  business and our earnings  could be materially and
adversely affected.

Loss of key members of our management  could adversely affect our business while
we attempt to find their replacements.

         We depend on the continued  employment  and  performance  of Wallace C.
Sparkman,  our Chairman,  Stephen C. Taylor,  our  President,  Earl R. Wait, our
Treasurer and Chief Financial Officer,  and other key members of our management.
If any of our key managers  resigns or becomes unable to continue in his present
role and is not adequately replaced, our business operations could be materially
adversely  affected.  We do not maintain any "key man" life insurance for any of
our officers.

We must evaluate our intangible assets annually for impairment.

         Our   intangible   assets  are   recorded  at  cost  less   accumulated
amortization  and consist of goodwill  and patent  costs.  Through  December 31,
2001,  goodwill was amortized using the  straight-line  method over 15 years and
patent costs were amortized over 13 to 15 years.

         In June 2001, the Financial Accounting Standards Board issued Statement
of  Financial  Accounting  Standards  No. 142,  "Goodwill  and Other  Intangible
Assets."  FAS 142  provides  that:  (1)  goodwill  and  intangible  assets  with
indefinite lives will no longer be amortized; (2) goodwill and intangible assets
with indefinite  lives must be tested for impairment at least annually;  and (3)
the amortization  period for intangible  assets with finite lives will no longer
be limited to forty years. In the event that we determine our intangible  assets
with indefinite  lives have been impaired,  we must record a write-down of those
assets on our  statement  of  operations  during the period of  impairment.  Our
determination of impairment will be based on various  factors,  including any of
the following factors, if they materialize:



                                       10


         o        significant under performance  relative to expected historical
                  or projected future operating results;

         o        significant  changes in the manner of our use of the  acquired
                  assets or the strategy for our overall business;

         o        significant negative industry or economic trends;

         o        significant decline in our stock price for a sustained period;
                  and

         o        our market capitalization relative to net book value.

         We  adopted  FAS  142 as of  January  1,  2002.  Based  on  independent
valuations in June 2003 and 2002 of our reporting units with goodwill,  adoption
of FAS 142 has not had a material adverse effect on us through at least 2003. In
the future it could result in impairments of our intangible  assets or goodwill.
We expect to continue to amortize our  intangible  assets with finite lives over
the same time periods as previously used, and we will test our intangible assets
with  indefinite  lives for impairment at least once each year. In addition,  we
are required to assess the  consumptive  life, or longevity,  of our  intangible
assets with finite lives and adjust their amortization periods  accordingly.  As
of March 31,  2005,  we had an  aggregate  of  approximately  $4,220,000  of net
intangible  assets.  We expect the carrying value of net intangible assets could
increase  significantly if we acquire additional  businesses.  Any impairment in
future periods of those assets, or a reduction in their consumptive lives, could
materially  and  adversely  affect our  statement of  operations  and  financial
position.

Provisions  contained in our  governing  documents  could hinder a change in our
control.

         Our articles of  incorporation  and bylaws contain  provisions that may
discourage acquisition bids and may limit the price investors are willing to pay
for our common  stock and  warrants.  Our articles of  incorporation  and bylaws
provide that:

         o        directors   will  be  elected  for  three-year   terms,   with
                  approximately one-third of the board of directors standing for
                  election each year;

         o        cumulative voting is not allowed,  which limits the ability of
                  minority shareholders to elect any directors;

         o        the   unanimous   vote  of  the  board  of  directors  or  the
                  affirmative  vote of the  holders  of not less than 80% of the
                  votes  entitled  to be  cast  by the  holders  of  all  shares
                  entitled to vote in the  election of  directors is required to
                  change the size of the board of directors; and

         o        directors may only be removed for cause by holders of not less
                  than 80% of the votes entitled to be cast on the matter.

         Our board of  directors  has the  authority to issue up to five million
shares  of  preferred  stock.  The board of  directors  can fix the terms of the
preferred stock without any action on the part of our shareholders. The issuance
of  shares  of  preferred  stock  may  delay  or  prevent  a change  in  control
transaction.  In addition,  preferred stock could be used in connection with the
board of  director's  adoption of a  shareholders'  rights plan (also known as a



                                       11


poison  pill),  which  would make it much more  difficult  to effect a change in
control  of us  through  acquiring  or  controlling  blocks  of our  stock.  Our
directors and officers as a group beneficially own stock. Although this is not a
majority of our stock,  it confers  substantial  voting power in the election of
directors and  management of us. This would make it difficult for other minority
shareholders  to effect a change in control or otherwise  extend any significant
control  over our  management.  This may  adversely  affect the market price and
interfere with the voting and other rights of our common stock.

You may suffer  substantial  dilution upon the exercise of outstanding  warrants
and options.

         As of March  31,  2005,  we had  outstanding  a  significant  number of
warrants and options to purchase  shares of our common stock.  If these warrants
or options are  exercised,  your  percentage  ownership  in Natural Gas Services
Group will be diluted and the price per share of our common  stock may  decline.
We have

         o        issued  warrants to purchase up to 2,347,660  shares of common
                  stock; and

         o        granted  options to  purchase  up to 130,500  shares of common
                  stock.


Under our employee and director  stock  option  plans,  we may grant  options to
purchase  up to an  additional  19,500  shares  of  common  stock.  All  of  our
outstanding  warrants and options have exercise prices below $11.75, the closing
sale price of our common stock on July 5, 2005. Sales of substantial  amounts of
common  stock,  or a  perception  that such sales could occur,  could  adversely
affect the  market  price of the common  stock and could  impair our  ability to
raise capital through the sale of our equity securities.


If we issue  debt or  equity  securities,  you may lose  certain  rights  and be
diluted.

         If we raise funds in the future  through the issuance of debt or equity
securities, the securities issued may have rights and preferences and privileges
senior to those of holders of our common stock,  and the terms of the securities
may impose  restrictions  on our  operations or dilute your ownership in Natural
Gas Services Group.

We do not  intend  to pay,  and  have  restrictions  upon  our  ability  to pay,
dividends on our common stock.

         We have not paid cash  dividends  in the past and do not  intend to pay
dividends on our common  stock in the  foreseeable  future.  Net income from our
operations, if any, will be used for the development of our business,  including
capital  expenditures,  and to retire debt. In addition,  our bank loan facility
contains restrictions on our ability to pay cash dividends on our common stock.

We have a comparatively  low number of shares of common stock  outstanding  and,
therefore,  our common  stock may suffer from limited  liquidity  and its prices
will likely be volatile and its value may be adversely affected.

         Because of our relatively  low number of  outstanding  shares of common
stock,  the  trading  price of our  common  stock  will  likely  be  subject  to
significant price fluctuations and limited liquidity.  This may adversely affect
the value of your  investment.  In  addition,  our common  stock  price could be
subject to  fluctuations  in  response  to  variations  in  quarterly  operating
results,  changes in  management,  future  announcements  concerning us, general
trends in the industry  and other  events or factors as well as those  described
above.



                                       12


The sale of stock by the selling shareholders may depress our stock price.

         Under this prospectus,  the selling shareholders may sell up to 701,171
of their shares of our common  stock,  representing  approximately  10.2% of our
outstanding common stock at the date of this prospectus. The sale of substantial
amounts of our stock owned by the selling  shareholders in the public market, or
the belief  that these  sales may occur,  could  reduce the market  price of our
stock,  making it more difficult for us to raise funds through future  offerings
of our common stock and to acquire businesses using our stock as consideration.


                           FORWARD LOOKING STATEMENTS

         Some  statements   contained  in  this  prospectus,   any  accompanying
prospectus   supplement,   and  the  documents  incorporated  by  reference  are
"forward-looking statements" within the meaning of Section 27A of the Securities
Act of 1933 (or  Securities  Act) and Section  21E of the  Exchange  Act.  These
statements  include,  without  limitation,  statements  relating  to oil and gas
prices,  demand for oil and gas, budgets,  business  strategies and other plans,
intentions and objectives of our management for future operations and activities
and other such  matters.  The words  "believe",  "budget",  "plan",  "estimate",
"expect", "intend", "strategy", "project", "will", "could", "may", "anticipate",
"continue"  and similar  expressions  identify  forward-looking  statements.  We
believe the  assumptions  and  expectations  reflected in these  forward-looking
statements  are  reasonable.  However,  we cannot  give any  assurance  that our
expectations  will  prove  to be  correct  or that  we will be able to take  any
actions that are presently planned.  Actual results could differ materially from
those expressed in the forward-looking statements. Factors that could cause such
a difference include:

         o        fluctuations in prices of oil and gas;

         o        future capital requirements and availability of financing;

         o        competition;

         o        general economic conditions;

         o        governmental regulations;

         o        receipt of amounts owed to us by our customers;

         o        events similar to 911; and

         o        fluctuations in interest rates and availability of capital.

         You  are  cautioned  not  to  place  undue   reliance  on  any  of  our
forward-looking  statements,  which speak only as of the date of the document or
in the case of documents incorporated by reference, the date of those documents.






                                       13


                                 USE OF PROCEEDS

         We will not receive any  proceeds  from the sale of our common stock by
the selling  shareholders.  However, we will receive the proceeds,  if exercised
(other than by cashless  exercise),  from warrants to purchase 582,203 shares of
common stock held by the selling shareholders.


               ISSUANCE OF SECURITIES TO THE SELLING SHAREHOLDERS

         The  selling  shareholders  received  the  securities  offered  in this
prospectus pursuant to the following transactions.

         In early 2001, in a private  placement we issued units comprised of 10%
Subordinated  Notes and Warrants to purchase up to 616,175  shares of our common
shock to the selling shareholders.  The warrants issued in the private placement
have a term of five years and are  exercisable at $3.25 per share.  The warrants
can be  exercised by paying cash,  or by way of  "cashless  exercise"  whereby a
portion of the shares  underlying the warrant are used, at the fair market value
of our common stock on the date of exercise,  to pay the exercise  price for the
remaining shares underlying the warrant.

         In March 2001,  we issued  warrants to  purchase  68,524  shares of our
common  stock  at  $2.50  per  share  in  exchange   for  persons   guaranteeing
approximately  $1,749,000  of our debt.  The warrants can be exercised by paying
cash,  or by way  of  "cashless  exercise"  whereby  a  portion  of  the  shares
underlying the warrant are used, at the fair market value of our common stock on
the  date of  exercise,  to pay the  exercise  price  for the  remaining  shares
underlying the warrant.  The warrants expire on December 31, 2006, and they were
issued  to the  following  persons  for  guaranteeing  the  amount  of our  debt
indicated:

                                    Number of Shares                Amount of
     Name                          Underlying Warrants           Debt Guaranteed


     Wallace O. Sellers(1)               21,936                     $548,399
     Wallace C. Sparkman(2)              21,467                      536,671
     CAV-RDV, Ltd.(3)                    15,756                      393,902
     Richard L. Yadon                     9,365                      234,121
---------------------------

     (1)  Mr. Sellers is a former Director of the company.
     (2)  Wallace  C.  Sparkman  is our  Chairman  of the  Board.  Mr.  Sparkman
          subsequently  transferred  his warrants for 21,467 shares to Diamond S
          DGT,  a  trust  of  which  Scott  W.  Sparkman  is the  trustee  and a
          beneficiary.  Wallace C. Sparkman has represented to us that he has no
          beneficial interest in Diamond S DGT.
     (3)  CAV-RDV,  Ltd., is a Texas limited  partnership for the benefit of the
          children of Wayne L. Vinson, our former Chief Executive Officer.


         In April 2002,  we issued  warrants to  purchase  16,472  shares of our
common  stock at $3.25 per share in  exchange  for  three  persons  guaranteeing
approximately  $824,000 of our debt.  The  warrants  can be  exercised by paying
cash,  or by way  of  "cashless  exercise"  whereby  a  portion  of  the  shares
underlying the warrant are used, at the fair market value of our common stock on
the  date of  exercise,  to pay the  exercise  price  for the  remaining  shares
underlying the warrant.  The warrants expire on December 31, 2007, and they were
issued  to the  following  persons  for  guaranteeing  the  amount  of our  debt
indicated:



                                       14


                                  Number of Shares          Amount of Additional
     Name                        Underlying Warrants          Debt Guaranteed
     ----                        -------------------          ---------------


     Wallace O. Sellers(1)              9,032                $  451,601
     CAV-RDV, Ltd.(2)                   2,122                   106,098
     Richard L. Yadon(1)                5,318                   265,879
---------------------------

(1)      Mr. Yadon serves as a director on our Board of Directors.  Mr.  Sellers
         is a former director of the company.


(2)      CAV-RDV,  Ltd., is a Texas limited  partnership  for the benefit of the
         children of Wayne L. Vinson, our former Chief Executive Officer.


         We will not receive any proceeds in connection  with the sale of shares
by the selling shareholders listed below; however, we will receive proceeds from
any cash exercise of the warrants.

         Although not required to do so, we have filed a registration statement,
to  which  this  prospectus  forms  a part,  in  order  to  permit  the  selling
shareholders to resell to the public the shares of common stock they have or may
acquired pursuant to the exercise of the warrants.

         We will pay all expenses of registering the shares under the Securities
Act,  including all registration,  listing and filing fees,  printing  expenses,
fees and  disbursements of our counsel,  expenses of any special audits incident
to or  required  by  the  registration,  and  expenses  of  complying  with  the
securities or blue sky laws of any jurisdictions.  The selling shareholders will
pay all discounts,  brokerage fees, commissions and expenses for any shares that
are registered and that they sell.












                                       15




                              SELLING SHAREHOLDERS

         The following table sets forth information provided by the selling
shareholders about the ownership of our common stock by the selling shareholders
before and after the offering covered by this prospectus.

                                            Shares                           Shares        Percentage of Shares
                                         Beneficially    Shares Being     Beneficially      Beneficially Owned
                                            Owned         Offered in         Owned         ---------------------
                                           Before             The             After        Before       After
Name                                     Offering(1)      Offering(2)      Offering(2)     Offering     Offering
----                                     -----------      -----------      -----------     --------     --------
                                                                                                          
Robert A. Street                            10,000          10,000             -0-         *            *
William E. Beggs                            10,000          10,000             -0-         *            *
Gary W. and Theresa L. Boening              24,400          20,000           4,400         *            *
Alvin R. Bonnette Revocable Trust(3)        75,900          68,000           7,900         1.1          *
The Burns Partnership(4)                   176,000          10,000         166,000         2.6          2.4
Butera Family Trust(5)                      58,000          24,000          34,000         *            *
Joseph E. Carothers                         29,172          18,000          11,172         *            *
CAV-RDV, Ltd.(6)                           177,878          17,878         160,000         2.6          2.4
Charles Curtis                              78,000          40,000          38,000         1.7          *
Leslie W. David Trust(7)                    11,600          10,000           1,600         *            *
Loretta J. David-Roth IRA                   11,600          10,000           1,600         *            *
Diamond S. DGT(8)                          496,467          21,467         475,000         7.3          7.0
Robert C. Dixon/IRA                         37,900          10,000          27,900         *            *
Alvin J. Donius                             10,000          10,000             -0-         *            *
Zenas N. Gurley                            166,471          10,471         156,000         2.5          2.3
William F. Hughes(9)                       247,000          60,000         187,000         3.6          2.7
Roy A. Johnson Revocable Trust(10)          12,000          10,000           2,000         *            *
Albert W. Karnath                           26,800          10,000          16,800         *            *
John Karnath                                10,000          10,000             -0-         *            *
Lorie Karnath                               10,000          10,000             -0-         *            *
Paul M.Karnath                              10,000          10,000             -0-         *            *
Alan Kurus                                  33,704          31,704           2,000         *            *
Elise L. Lyon Revocable Living Trust        10,000          10,000             -0-         *            *
Utd. 9/23/96(11)                                                                           
Sally Jo Maisano                            36,000          26,000          10,000         *            *
Darell&Thordis Norris Trust(12)             16,000          10,000           6,000         *            *
Mary Jane Peck                              26,800          20,000           6,800         *            *
B. Kay Phillips                             10,000          10,000             -0-         *            *
Sharon L. Pitken-IRA                       112,000          36,000          76,000         1.6          1.1
G Five Development LLC(13)                  82,000          32,000          50,000         1.2          *
Earl W. Sauder Trust(14)                    32,408          20,000          12,408         *            *
David C. Shatzer                            55,200          20,000          35,200         *            *
Gary E. Schenkel                            11,000          10,000           1,000         *            *
Wallace O. Sellers(15)                     693,159          30,968         662,191         10.2         9.8
Donald L. Smallwood                         10,000          10,000             -0-         *            *
Kipp/Glenda Jo Smallwood                    10,000          10,000             -0-         *            *
Lazaros/Patricia Voreadis                   30,000          10,000          20,000         *            *
Richard L. Yadon(16)                       299,183          14,683         284,500         4.4          4.2
                                           -------          ------         -------           
TOTALS                                   3,156,642         701,171       2,455,471        
* Less than 1%





                                       16

-----------------
(1)  Beneficial  ownership  is  determined  in  accordance  with  Rule  13d-3(d)
promulgated by the SEC under the Exchange Act, which includes shares  underlying
the  warrants and any other  securities  which are  convertible  into our common
stock within 60 days of the date of this  prospectus.  The  calculations  of the
percentages of shares  beneficially owned are based upon 6,782,764 shares of our
common  stock  outstanding  at March 31,  2005 and  assume the  exercise  of the
warrants  (which are  exercisable  for shares of our common  stock) held by that
selling shareholder.
(2) The selling shareholders may offer shares under this prospectus from time to
time and may elect to sell none, some or all of the shares set forth above. As a
result,  we cannot  estimate  the number of shares of our common  stock that the
selling shareholders will beneficially own after termination of sales under this
prospectus.  For  purposes  of this table,  however,  we have  assumed  that the
selling shareholders sell all of their shares issued or issuable pursuant to the
warrants.  In addition,  the selling shareholders may have sold,  transferred or
otherwise disposed of all or a portion of their shares of our common stock since
the date on which they provided information for this table.
(3) Alvin R.  Bonnette is the Trustee of the Alvin R. Bonnette  Revocable  Trust
and consequently has voting and investment control over the shares.  Each of Mr.
Bonnette's six children are beneficiaries under the trust.
(4) William Burns, David Burns,  Michael Burns, Barbara Burns, and Jeffrey Burns
are the  members  and  beneficial  owners  of The Burns  Partnership,  a general
partnership, and each such person consequently has voting and investment control
over the shares.
(5) Roy T. Butera is trustee of the Butera  Family  Trust and  consequently  has
voting and  investment  control  over the  shares.  Each of Mr.  Butera's  three
children are beneficiaries under the trust.
(6) The children of Wayne L. Vinson, our former Chief Executive Officer, are the
beneficial owners of CAV-RDV, Ltd., at Texas Limited Partnership.
(7) Leslie W. David is trustee of the Leslie W. David Trust and consequently has
voting and investment  control over the shares. Mr. David's wife, Loretta David,
is the beneficiary under the trust.
(8) The  warrant  for 21,467  shares of our common  stock at $6.25 per share was
initially issued to Wallace C. Sparkman, our Chairman of the Board. Mr. Sparkman
subsequently  transferred  his warrants  for 21,467  shares to Diamond S. DGT, a
trust of which Scott W.  Sparkman is the trustee and a  beneficiary.  Wallace C.
Sparkman has represented to us that he has no beneficial  interest in Diamond S.
DGT.
(9) The  247,000  beneficially  owned  shares  include  (i) 1,500  shares  owned
directly by William F. Hughes,  Jr., (ii) 180,500  shares held by the William F.
and  Cheryl C.  Hughes  Family  Trust in which  William  and  Cheryl  Hughes are
co-trustees  and  consequently  share  voting and  investment  over the  shares;
William  and Cheryl  Hughes are also  beneficiaries  under the trust  along with
their two  children,  and (iii) 5,000  shares  issuable  upon  exercise of stock
options ranging from $5.55 to $9.34 per share,  held by William F. Hughes,  Jr.,
and (iv) the 60,000 shares registered herein which are issuable upon exercise of
a stock warrant at $3.25 per share, held by William F. Hughes, Jr.
(10) Roy A.  Johnson  is  trustee  of the Roy A.  Johnson  Revocable  Trust  and
consequently  has voting and  investment  control  over the shares.  Each of Mr.
Johnson's two children are beneficiaries under the trust.
(11) Elise S. Lyon is trustee of the Elise S. Lyon  Revocable  Living  Trust Utd
9/23/96 and consequently has voting and investment control over the shares. Each
of Ms. Lyon's three children are beneficiaries under the trust.
(12) Darell Norris and Thordis Norris are co-trustees and  beneficiaries  of the
Darell & Thordis  Norris  Trust and  consequently  share  voting and  investment
control over the shares.
(13)  Roland  W.  Gentner,  a  resident  of Rapid  City,  South  Dakota,  is the
beneficial  owner of G Five  Development  LLC, a South Dakota limited  liability
company. Mr. Gentner beneficially owns 369,000 shares of our common stock.
(14) Earl W. Sauder is trustee of the Earl W. Sauder Trust and  consequently has
voting and investment control over the shares.  Mr. Sauder's wife,  children and
grandchildren are beneficiaries.
 
(15)  Wallace O.  Sellers  is a former  Director  of our  Company.  The  693,159
beneficially  owned shares  include (i) 134,877 shares owned directly by Wallace
O. Sellers,  (ii) 158,600 shares owned through Mr.  Sellers'  wife,  (iii) 7,500
shares  issuable upon exercise of stock options  ranging from $3.88 to $9.34 per
share,  (iv)  196,091  shares  held in a trust in which Mr.  Sellers'  wife is a
lifetime  beneficiary and an unrelated third party acts as trustee,  (v) 196,091
shares held in a trust in which Mr.  Sellers' wife is a contingent  beneficiary,
and an unrelated third party acts as trustee. Mr. Sellers disclaims ownership of
all shares held in the two trusts.

(16)  Richard L. Yadon is a Director of our  Company.  The 299,193  beneficially
owned shares include (i) 279,500 shares owned directly by Richard L. Yadon, (ii)
5,000 shares issuable upon exercise of stock options ranging from $5.55 to $9.34
per share,  and (iii) 14,683 shares  issuable upon exercise of stock warrants at
$2.50 and $3.25 per share.
--------------------------------



                                       17


                              PLAN OF DISTRIBUTION

         The shares of common stock  covered by this  prospectus  may be offered
and sold  from  time to time by the  selling  shareholders.  The  term  "selling
shareholders"    includes    donees,    pledgees,     transferees    or    other
successors-in-interest selling shares received after the date of this prospectus
from a selling shareholder as a gift, pledge,  shareholder distribution or other
non-sale related transfer. The selling shareholders will act independently of us
in making decisions with respect to the timing, manner and size of each sale.

         Sales  of  shares  by the  selling  shareholders  referred  to in  this
prospectus  may be made  from  time to time in one or more  transactions  on the
American Stock Exchange, in the over-the-counter market or any other exchange or
quotation system on which shares of our common stock may be listed or quoted, in
negotiated  transactions or in a combination of any such methods of sale.  Sales
may be at fixed prices that may be changed,  at market prices  prevailing at the
time  of  sale,  at  prices  related  to such  prevailing  market  prices  or at
negotiated  prices.  The shares may be offered  directly to  purchasers or to or
through  underwriters  or agents  designated  from time to time or to or through
brokers or dealers, or through any combination of these methods of sale.

         The methods by which the shares may be sold include:

         o        block trades  (which may involve  crosses) in which the broker
                  or dealer will attempt to sell the securities as agent but may
                  position  and  resell a portion of the block as  principal  to
                  facilitate the transaction;

         o        purchases by a broker or dealer as principal and resale by the
                  broker or dealer for its own account under this prospectus;

         o        exchange   distributions   or   secondary   distributions   in
                  accordance  with the rules of the American  Stock  Exchange or
                  other relevant markets;

         o        short sales, ordinary brokerage  transactions and transactions
                  in which the broker solicits purchasers;

         o        transactions in options,  swaps or other derivatives,  whether
                  exchange-listed or otherwise;

         o        firm commitment or best efforts underwritings; and

         o        privately negotiated transactions.

         In addition,  sales not covered by this  prospectus may also be made by
the selling  shareholders under Rule 144 or another  applicable  exemption under
the Securities Act.

         From time to time the selling  shareholders may distribute a portion or
all of their shares to their owners. In the event of such a distribution, and to
the  extent  these  owners  intend  to use this  prospectus  to sell any of such
shares,  if required  these owners will be  identified  in a supplement  to this
prospectus  filed  with the  SEC.  Furthermore,  to the  extent  required,  this
prospectus also may be amended or  supplemented  from time to time to describe a
specific  plan  of  distribution  or any  material  arrangement  that a  selling
shareholder  has entered into for the sale of shares,  including  the details of
any underwritten distribution.

         In connection with  distributions  of shares or otherwise,  the selling
shareholders may enter into hedging  transactions  with  broker-dealers or other
agents.  In connection with these  transactions,  broker-dealers or other agents
may engage in short sales of shares in the course of hedging the positions  they
assume with the selling  shareholders.  The selling  shareholders  may also sell
shares short and  redeliver the shares to close out their short  positions.  The


                                       18


selling  shareholders  may also enter  into  option or other  transactions  with
broker-dealers or other financial institutions that require the delivery to that
broker-dealer  or  other  financial   institution  of  shares  offered  by  this
prospectus,  which shares that broker-dealer or other financial  institution may
resell  under this  prospectus  (as  supplemented  or  amended  to  reflect  the
transaction).  The  selling  shareholders  may also  pledge or grant a  security
interest  in  shares  and,  upon a default  in the  performance  of the  secured
obligation,  the pledgee or secured party may affect sales of the pledged shares
under this prospectus (as supplemented or amended to reflect the transaction).

         In effecting  sales,  broker-dealers  or agents  engaged by the selling
shareholders   may   arrange   for   other    broker-dealers   to   participate.
Broker-dealers,  underwriters  or agents may receive  commissions,  discounts or
concessions from the selling  shareholders  and/or  purchasers of the shares for
whom they may act as agents.

         In  offering  the  shares  covered  by  this  prospectus,  the  selling
shareholders  and any  broker-dealers,  underwriters or agents who execute sales
for the  selling  shareholders  may be deemed to be  "underwriters"  within  the
meaning of the  Securities  Act in  connection  with these  sales.  Any  profits
realized by the selling  shareholders and the compensation of any broker-dealer,
underwriter or agent may be deemed to be underwriting discounts and commissions.
No underwriter, broker-dealer or agent has been engaged by us in connection with
the distribution of the shares.

         To comply with the securities  laws of certain  states,  if applicable,
the  shares  must be sold in those  jurisdictions  only  through  registered  or
licensed brokers or dealers.  In addition,  in certain states the shares may not
be sold unless they have been registered or qualified for sale in the applicable
state or an exemption  from the  registration  or  qualification  requirement is
available and is complied with.

         The  selling  shareholders  and any  other  person  participating  in a
distribution  of the shares  covered by this  prospectus  will be subject to the
applicable  provisions  of the  Exchange  Act  and  the  rules  and  regulations
thereunder.  Regulation  M of the Exchange Act may limit the timing of purchases
and  sales of shares  by the  selling  shareholders  and any  other  person.  In
addition,  Regulation M may  restrict  the ability of any person  engaged in the
distribution of the shares to engage in market-making activities with respect to
our  common  stock  for  a  period  of up  to  five  business  days  before  the
distribution.


                                  LEGAL MATTERS

         The validity  under  Colorado law of the shares will be passed upon for
us by Jackson Kelly PLLC, Denver, Colorado.


                                     EXPERTS

         HEIN & ASSOCIATES LLP,  independent  registered public accounting firm,
have  audited our  consolidated  balance  sheet at December  31,  2004,  and the
consolidated statements of income,  shareholders' equity and cash flows for each
of the two years ended December 31, 2004 and 2003, as set forth in their report,
which  is  incorporated  in  this  prospectus  by  reference.  Our  consolidated
financial  statements are incorporated by reference in reliance on their report,
given on their authority as experts in accounting and auditing.





                                       19


================================================
          We  have  not  authorized  any
dealer,  salesperson  or other person to
give  any  information  or to  make  any
representation  not  contained  in  this
prospectus.  This  prospectus  does  not
constitute   an  offer  to  sell,  or  a
solicitation  of an  offer  to buy,  any
offer or  solicitation  by anyone in any
jurisdiction not authorized, or in which
the  person  making  such  an  offer  or
solicitation  is not  qualified to do so
or to any person to whom it is  unlawful
to make  such an offer or  solicitation.
By delivery of this prospectus we do not
imply  that  there has been no change in
our affairs or that the  information  in
this  prospectus  is  correct  as of any
time subsequent to its date.
================================================
                                                            NATURAL GAS SERVICES
           TABLE OF CONTENTS                                GROUP, INC.


                                                    Page

Where You Can Find Additional Information             2
Incorporation of Documents by Reference               2
About Natural Gas Services Group, Inc.                3                 
                                                                --------------
Risk Factors                                          4         
Forward Looking Statements                           13           PROSPECTUS
Use of Proceeds                                      14                   
                                                                --------------
Issuance of Securities to the Selling Shareholders   14       
Selling Shareholders                                 16
Plan of Distribution                                 17
Legal Matters                                        19
Experts                                              19





                                                                July ___, 2005
















                                       20


                                     PART II


                     INFORMATION NOT REQUIRED IN PROSPECTUS


Item 14. Other Expenses of Issuance and Distribution.

         Expenses payable by us in connection with the issuance and distribution
of the securities being registered hereby are as follows:

         Securities and Exchange Commission registration fee          $      855
         Accounting fees and expenses                                 $    2,000
         Legal fees and expenses                                      $    7,500
         Printing expenses                                            $    1,000
         Transfer agent fees                                          $      500
         Miscellaneous                                                $      145
                                                                      ----------
                                                                          
           Total                                                      $   12,000
                                                                      ==========
                                                              
         All of the  above  expenses  except  for the  Securities  and  Exchange
Commission  registration  fee are  estimated.  All such  items  will be borne by
Natural Gas Services Group, Inc.

Item 15.  Indemnification of Directors and Officers.

         Section  7-109-102 of the Colorado  Business  Corporation Act permits a
Colorado  corporation to indemnify any director against liability if such person
acted in good faith and, in the case of conduct in an official capacity with the
corporation, that the director's conduct was in the corporation's best interests
and, in all other cases, that the director's conduct was at least not opposed to
the best interests of the corporation  or, with regard to criminal  proceedings,
the  director  had no  reasonable  cause to believe the  director's  conduct was
unlawful.

         Section  7-109-103 of the Colorado  Business  Corporation  Act provides
that,  unless limited by its articles of incorporation,  a Colorado  corporation
shall indemnify a person who was wholly successful,  on the merits or otherwise,
in the  defense of any  proceeding  to which the person was a party  because the
person is or was a director,  against reasonable expenses incurred by him or her
in connection with the proceeding.

         Section 3 of Article IX of our articles of incorporation  provides that
we shall  indemnify,  to the maximum extent permitted by law in effect from time
to time,  any person who is or was a  director,  officer,  agent,  fiduciary  or
employee of ours  against any claim,  liability  or expense  arising  against or
incurred by such person made party to a proceeding because such person is or was
a director, officer, agent, fiduciary or employee of ours or because such person
is or was serving  another  entity as a  director,  officer,  partner,  trustee,
employee,  fiduciary or agent at our request.  We further have the  authority to
the maximum extent permitted by law to purchase and maintain insurance providing
such indemnification.

         Article VI of our bylaws  provides for the  indemnification  of certain
persons.

         Insofar as indemnification for liabilities arising under the Securities
Act of 1933 may be permitted to our directors,  officers and controlling persons
pursuant to the foregoing provisions, or otherwise, we have been advised that in
the opinion of the Securities and Exchange  Commission such  indemnification  is
against  public  policy  as  expressed  in the  Securities  Act of 1933  and is,
therefore, unenforceable.




                                      II-1


Item 16. Exhibits.

         The  following  is a  list  of all  exhibits  filed  as  part  of  this
Registration Statement:

Exhibit
  No.          Description
-------        -----------


 5             Legal Opinion of Jackson Kelly PLLC (2)


 10.5          Form of Five-Year Warrants to Purchase Common Stock (1)

 23.1          Consent of Jackson Kelly PLLC (Included in Exhibit 5)

 23.2          Consent of HEIN & ASSOCIATES LLP*

 24            Power of Attorney (see the signature page) (2)
---------------------------                           
*Filed herewith
(1)  Incorporated by reference to the Company's  Registration  Statement on Form
SB-2 (No. 333-88314)

(2) Previously filed

Item 17.  Undertakings.

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, as amended;

                  (ii)     To  reflect  in the  prospectus  any  facts or events
                           arising after the effective date of this 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 this 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  Securities  and  Exchange
                           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 Fee" table in the effective registration
                           statement; and

                  (iii)    To include any material  information  with respect to
                           the plan of distribution not previously  disclosed in
                           this Registration Statement or any material change to
                           such information in this Registration Statement.



                                      II-2


                           Provided, however, that paragraphs (1)(i) and (1)(ii)
                           do  not  apply  if  the  information  required  to be
                           included  in  a  post-effective  amendment  by  those
                           paragraphs  is  contained in periodic  reports  filed
                           with or  furnished  to the  Securities  and  Exchange
                           Commission by the  Registrant  pursuant to Section 13
                           or Section  15(d) of the  Securities  Exchange Act of
                           1934, as amended,  that are incorporated by reference
                           in this Registration Statement.

         (2)      That, for the purpose of determining  any liability  under the
                  Securities  Act, each such  post-effective  amendment shall be
                  deemed  to be a new  registration  statement  relating  to the
                  securities offered herein, 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.

         The  undersigned  Registrant  hereby  undertakes  that, for purposes of
determining  any  liability  under  the  Securities  Act,  each  filing  of  the
Registrant's  Annual  Report  pursuant to Section  13(a) or Section 15(d) of the
Exchange Act (and, where  applicable,  each filing of an employee benefit plan's
annual  report   pursuant  to  Section  15(d)  of  the  Exchange  Act)  that  is
incorporated by reference in this Registration Statement 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.

         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  above,  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 Securities 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 and will be governed by the final adjudication of such issue.








                                      II-3


                                   SIGNATURES


         In accordance with 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 of filing on Form S-3 and has duly caused this Amendment No.
1 to this registration  statement to be signed on its behalf by the undersigned,
thereunto  duly  authorized,  in the City of Midland,  State of Texas on July 8,
2005.


                                      NATURAL GAS SERVICES GROUP, INC.


                                       /s/ Stephen C. Taylor                
                                      ------------------------------------------
                                      Stephen C. Taylor, President and Principal
                                      Executive Officer


                                       /s/ Earl R. Wait                         
                                      ------------------------------------------
                                      Earl R. Wait, Principal Financial and
                                      Accounting Officer


         Pursuant  to the  requirements  of the  Securities  Act of  1933,  this
registration statement was signed by the following persons in the capacities and
on the dates indicated:


Signature                                Title                          Date
---------                                -----                          ----



/s/ EARL R. WAIT                        Director (Chairman)         July 8, 2005
-----------------------
Attorney-in-fact for
Wallace C. Sparkman


/s/ STEPHEN C. TAYLOR                   Director                    July 8, 2005
-----------------------
Stephen C. Taylor


/s/EARL R. WAIT                         Director                    July 8, 2005
-----------------------
Attorney-in-fact for
Charles G. Curtis


/s/ EARL R. WAIT                        Director                    July 8, 2005
-----------------------
Attorney-in-fact for
William F. Hughes


/s/ EARL R. WAIT                        Director                    July 8, 2005
-----------------------
Attorney-in-fact for
Gene A. Strasheim





                                      II-4



/s/ EARL R. WAIT                        Director                    July 8, 2005
-----------------------
Attorney-in-fact for
Richard L. Yadon


/s/ EARL R. WAIT                        Director                    July 8, 2005
-----------------------
Attorney-in-fact for
Paul Hensley













                                      II-5


                                  EXHIBIT INDEX



Exhibit
  No.                            Description
-------                          -----------


  5               Legal Opinion of Jackson Kelly PLLC (2)


 10.5             Form of Five-Year Warrants to Purchase Common Stock (1)

 23.1             Consent of Jackson Kelly PLLC (Included in Exhibit 5)

 23.2             Consent of HEIN & ASSOCIATES LLP*

 24               Power of Attorney (see the signature page) (2)
---------------------                           
*Filed herewith
(1)  Incorporated by reference to the Company's  Registration  Statement on Form
SB-2 (No. 333-88314)
(2) Previously filed