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

                                  FORM 10-KSB/A

                                (Amendment No. 2)

[X]  ANNUAL REPORT UNDER SECTION 13 OR 15(d) OF THE  SECURITIES  EXCHANGE ACT OF
     1934

                   For the fiscal year ended December 31, 2004

[_]  TRANSITION REPORT UNDER SECTION 13 OR 15(d) OF THE SECURITIES  EXCHANGE ACT
     OF 1934

          For the transition period from _____________ to _____________

                         Commission file number 1-31398

                        NATURAL GAS SERVICES GROUP, INC.
                 (Name of small business issuer in its charter)

                 Colorado                                        75-2811855
      (State or other jurisdiction of                         (I.R.S. Employer
incorporation or organization)                               Identification No.)

      2911 South County Road 1260
               Midland, Texas                                      79706
(Address of principal executive offices)                         (Zip Code)

                                 (432) 563-3974
                (Issuer's telephone number, including area code)

         Securities registered under Section 12(b) of the Exchange Act:

                           Common Stock $.01 Par Value
                                (Title of Class)


                        Warrants to Purchase Common Stock
                                (Title of Class)

       Securities registered under Section 12(g) of the Exchange Act: None


         Check whether the issuer (1) filed all reports  required to be filed by
Section 13 or 15(d) of the  Exchange  Act during the past 12 months (or for such
shorter period that the  registrant was required to file such reports),  and (2)
has been subject to such filing requirements for the past 90 days. Yes X  No
                                                                      ---   ---

         Check if there is no  disclosure  of  delinquent  filers in response to
Item 405 of  Regulation  S-B contained in this form,  and no disclosure  will be
contained,  to the best of the  registrant's  knowledge,  in definitive proxy or
information statements incorporated by reference in Part III of this Form 10-KSB
or any amendment to this Form 10-KSB. [X]

         State issuer's revenue for its most recent fiscal year: $15,958,199

         The aggregate  market value of the voting and non-voting  common equity
held by non-affiliates  at March 23, 2005,  computed by reference to the closing
price of $10.76 per share on the American Stock Exchange, was $47,676,914.

         The number of shares  outstanding  of each of the  issuer's  classes of
common equity on March 23, 2005, was 6,765,764.

                       Documents Incorporated by Reference
                                      None

           Transitional Small Business Disclosure Format Yes    No X
                                                            ---   ---
================================================================================

<PAGE>

                                EXPLANATORY NOTE

         We are filing this  Amendment No. 2 to our Annual Report on Form 10-KSB
in  response to comments  received  by us from the Staff of the  Securities  and
Exchange Commission.  Unless otherwise stated, all information contained in this
amendment is as of March 30, 2005, the filing date of our original Annual Report
on Form 10-KSB for the fiscal year ended  December 31, 2004. As a result of this
amendment,  Natural  Gas  Services  Group,  Inc.  is filing as  exhibits to this
Amendment  No. 2 on Form 10-KSB the  certifications  pursuant to Section 302 and
906 of the  Sarbanes-Oxley  Act of 2002.  This  Amendment No. 2 on Form 10-KSB/A
does not change our previously reported financial statements and other financial
disclosures.

         Items included in the original Form 10-KSB, as amended by Amendment No.
1 to Form 10-KSB filed with the  Securities  and Exchange  Commission  on May 4,
2005,  that are not  included  herein are not amended and remain in effect as of
the date of the original  filing,  as amended by Amendment No. 1.  Additionally,
this Form  10-KSB/A does not purport to provide an update or a discussion of any
other  developments  subsequent to the original filing,  as amended by Amendment
No. 1.













                                       2
<PAGE>

Item 8A.  CONTROLS AND PROCEDURES

         Under the supervision and with the  participation of certain members of
Natural Gas'  management,  the chief  executive  officer and the chief financial
officer  evaluated the  effectiveness of the disclosure  controls and procedures
(as defined in Rules  13a-15(e) and 15d-15(e) of the Securities  Exchange Act of
1934, as amended (the "Exchange Act")) of Natural Gas Services Group, Inc. as of
December 31, 2004.  Based on this  evaluation,  the chief executive  officer and
chief  financial  officer  concluded that Natural Gas'  disclosure  controls and
procedures  were effective as of the end of the period covered by this report to
ensure that information  required to be disclosed by Natural Gas Services Group,
Inc. in the reports that it files under the Exchange Act is collected, processed
and disclosed within the time periods  specified in the  Commission's  rules and
forms.

         There  were no changes in Natural  Gas'  internal  controls  during the
fourth quarter of 2004 that have materially affected or are reasonably likely to
materially  affect Natural Gas' internal controls over financial  reporting.  In
addition,  to the knowledge of the chief  executive  officer and chief financial
officer there were no changes in other factors that could  significantly  affect
these controls  subsequent to the date of the most recent evaluation made by the
chief executive officer and chief financial officer.


















                                       3
<PAGE>

 Item 13.     EXHIBITS

         The  following  is a list of all  exhibits  filed as part of this  Form
10-KSB/A:

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


2.1               Purchase and Sale Agreement by and between Hy-Bon  Engineering
                  Company, Inc. and NGE Leasing, Inc. (Incorporated by reference
                  to Exhibit 2.1 of the Registrant's  Current Report on Form 8-K
                  dated  February  28,  2003 and filed with the  Securities  and
                  Exchange Commission on March 6, 2003)

3.1               Articles  of  Incorporation,   as  amended   (Incorporated  by
                  reference to Exhibit 3.1 of the 10QSB filed and dated November
                  10, 2004)

3.2               Bylaws  (Incorporated  by  reference  to  Exhibit  3.4  of the
                  Registrant's   Registration   Statement  on  Form  SB-2,   No.
                  333-88314)

4.1               Form of warrant  certificate  (Incorporated  by  reference  to
                  Exhibit 4.1 of the Registrant's Registration Statement on Form
                  SB-2, No. 333-88314)

4.2               Form of warrant agent agreement  (Incorporated by reference to
                  Exhibit 4.2 of the Registrant's Registration Statement on Form
                  SB-2, No. 333-88314)

4.3               Form  of  lock-up  agreement  (Incorporated  by  reference  to
                  Exhibit 4.3 of the Registrant's Registration Statement on Form
                  SB-2, No. 333-88314)

4.4               Form of  representative's  option for the  purchase  of common
                  stock  (Incorporated  by  reference  to  Exhibit  4.4  of  the
                  Registrant's   Registration   Statement  on  Form  SB-2,   No.
                  333-88314)

4.5               Form of  representative's  option for the purchase of warrants
                  (Incorporated  by reference to Exhibit 4.5 of the Registrant's
                  Registration Statement on Form SB-2, No. 333-88314)

4.6               Stockholders  Agreement,  dated  January 3, 2005 among Paul D.
                  Hensley,  Tony Vohjesus,  Jim Hazlett and Natural Gas Services
                  Group,  Inc.  (Incorporated by reference to Exhibit 4.3 of the
                  Registrant's From 8-K Report,  dated January 3, 2005, as filed
                  with the  Securities  and  Exchange  Commission  on January 7,
                  2005)



                                       4
<PAGE>

                  Executive  Compensation Plans and Arrangements (Exhibits 10.1,
                  10.24, 10.25 and 10.26)

10.1              1998 Stock Option Plan  (Incorporated  by reference to Exhibit
                  10.1 of the Registrant's  Registration Statement on Form SB-2,
                  No. 333-88314)

10.2              Asset Purchase  Agreement,  dated January 1, 2001, between the
                  Registrant and Great Lakes Compression,  Inc. (Incorporated by
                  reference  to Exhibit  10.2 of the  Registrant's  Registration
                  Statement on Form SB-2, No. 333-88314)

10.3              Exhibits  3(c)(1),  3(c)(2),   3(c)(3),   3(c)(4),   13(d)(1),
                  13(d)(2)  and  13(d)(3)  to Asset  Purchase  Agreement,  dated
                  January  1,  2001,  between  the  Registrant  and Great  Lakes
                  Compression,  Inc. (Incorporated by reference to Exhibit 10.14
                  of the Registrant's  Registration  Statement on Form SB-2, No.
                  333-88314)

10.4              Amendment to Guaranty  Agreement  between Natural Gas Services
                  Group, Inc. and Dominion Michigan  Production  Services,  Inc.
                  (Incorporated by reference to Exhibit 10.3 of the Registrant's
                  Registration Statement on Form SB-2, No. 333-88314)

10.5              Form of Series A 10% Subordinated  Notes due December 31, 2006
                  (Incorporated by reference to Exhibit 10.8 of the Registrant's
                  Registration Statement on Form SB-2, No. 333-88314)

10.6              Form  of   Five-Year   Warrants  to  Purchase   Common   Stock
                  (Incorporated by reference to Exhibit 10.9 of the Registrant's
                  Registration Statement on Form SB-2, No. 333-88314)

10.7              Warrants issued to Berry-Shino Securities,  Inc. (Incorporated
                  by reference to Exhibit 10.10 of the Registrant's Registration
                  Statement on Form SB-2, No. 333-88314)

10.8              Warrants   issued   to   Neidiger,    Tucker,   Bruner,   Inc.
                  (Incorporated   by   reference   to   Exhibit   10.11  of  the
                  Registrant's   Registration   Statement  on  Form  SB-2,   No.
                  333-88314)

10.9              Form of  warrant  issued in March 2001 for  guaranteeing  debt
                  (Incorporated   by   reference   to   Exhibit   10.12  of  the
                  Registrant's   Registration   Statement  on  Form  SB-2,   No.
                  333-88314)

10.10             Form of  warrant  issued in April 2002 for  guaranteeing  debt
                  (Incorporated   by   reference   to   Exhibit   10.13  of  the
                  Registrant's   Registration   Statement  on  Form  SB-2,   No.
                  333-88314)



                                       5
<PAGE>

10.11             Articles of Organization of Hy-Bon Rotary Compression, L.L.C.,
                  dated April 17, 2000  (Incorporated  by  reference  to Exhibit
                  10.18 of the Registrant's Registration Statement on Form SB-2,
                  No. 333-88314)

10.12             Regulations of Hy-Bon Rotary Compression, L.L.C. (Incorporated
                  by reference to Exhibit 10.19 of the Registrant's Registration
                  Statement on Form SB-2, No. 333-88314)

10.13             First  Amended  and  Restated  Loan   Agreement   between  the
                  Registrant  and  Western   National  Bank   (Incorporated   by
                  reference to Exhibit 10.1 of the  Registrant's  Current Report
                  on  Form  8-K,  dated  March  27,  2003  and  filed  with  the
                  Securities and Exchange Commission on April 14, 2003)

10.14             Form of Termination of Employment Agreement Letter relating to
                  the  Employment  Agreement  of  Alan  Kurus  (Incorporated  by
                  reference to Exhibit 10.25 of the  Registrant's  Annual Report
                  on Form 10-KSB for the fiscal year ended December 31, 2002)

10.15             Form of Termination of Employment Agreement Letter relating to
                  the  Employment  Agreement  of Wayne Vinson  (Incorporated  by
                  reference to Exhibit 10.26 of the  Registrant's  Annual Report
                  on Form 10-KSB for the fiscal year ended December 31, 2002)

10.16             Form of Termination of Employment Agreement Letter relating to
                  the  Employment   Agreement  of  Earl  Wait  (Incorporated  by
                  reference to Exhibit 10.27 of the  Registrant's  Annual Report
                  on Form 10-KSB for the fiscal year ended December 31, 2002)

10.17             Triple Net Lease  Agreement,  dated June 1, 2003,  between NGE
                  Leasing, Inc. and Steven J. & Katherina L. Winer (Incorporated
                  by  reference  to  Exhibit  10.17 of the  Registrant's  Annual
                  Report on Form 10-KSB for the fiscal year ended  December  31,
                  2003)

10.18             Lease  Agreement,  dated June 19,  2003,  between NGE Leasing,
                  Inc. and Wise Commercial Properties (Incorporated by reference
                  to Exhibit  10.18 of the  Registrant's  Annual  Report on Form
                  10-KSB for the fiscal year ended December 31, 2003)

10.19             Lease Agreement,  dated March 1, 2004,  between the Registrant
                  and the City of Midland,  Texas  (Incorporated by reference to
                  Exhibit 10.19 of the  Registrant's  Form 10-QSB for the fiscal
                  quarter ended June 30, 2004)



                                       6
<PAGE>

10.20             Second Amended and Restated Loan Agreement,  dated November 3,
                  2003,   between  the  Registrant  and  Western  National  Bank
                  (Incorporated   by   reference   to   Exhibit   10.20  of  the
                  Registrant's Form 10-QSB for the fiscal quarter ended June 30,
                  2004)

10.21             Securities  Purchase  Agreement,  dated July 20, 2004, between
                  the Registrant and CBarney Investments,  Ltd. (Incorporated by
                  reference to Exhibit 4.1 of the Registrant's Current Report on
                  Form 8-K dated July 20, 2004 and filed with the Securities and
                  Exchange Commission on July 27, 2004)

10.22             Stock Purchase Agreement, dated October 18, 2004, by and among
                  the  Registrant,  Screw  Compression  Systems,  Inc.,  Paul D.
                  Hensley,  Jim  Hazlett  and  Tony  Vohjesus  (Incorporated  by
                  reference to Exhibit 4.1 of the Registrant's Current Report on
                  Form 8-K dated October 18, 2004 and filed with the  Securities
                  and Exchange Commission on October 21, 2004)

10.23             Fourth  Amended and Restated Loan Agreement  (Incorporated  by
                  reference to Exhibit 10.1 of the  Registrant's  Current Report
                  on Form 8-K, dated March 14, 2005 as filed with the Securities
                  and Exchange Commission on March 18, 2005)

10.24             Employment  Agreement  between Paul D. Hensley and Natural Gas
                  Services  Group,  Inc.  (Incorporated  by reference to Exhibit
                  10.1 of the  Registrants  Form 8-K  Report,  dated  January 3,
                  2005, as filed with the Securities and Exchange  Commission on
                  January 7, 2005)

10.25             Employment Agreement between William R. Larkin and Natural Gas
                  Services  Group,  Inc.  (Incorporated  by reference to Exhibit
                  10.25 of the  Registrant's  Form  10-KSB for the  fiscal  year
                  ended  December 31, 2004,  and filed with the  Securities  and
                  Exchange Commission on March 30, 2005)

10.26             Promissory  Note,  dated  January  3,  2005,  in the  original
                  principal amount of $2,100,000.00 made by Natural Gas Services
                  Group,  Inc.  payable  to Paul  D.  Hensley  (Incorporated  by
                  reference to Exhibit 10.26 of the Registrant's Form 10-KSB for
                  the fiscal year ended  December 31,  2004,  and filed with the
                  Securities and Exchange Commission on March 30, 2005)

14.0              Code of Ethics  (Incorporated  by reference to Exhibit 14.0 of
                  the  Registrant's  Form  10-KSB  for  the  fiscal  year  ended
                  December 31, 2004,  and filed with the Securities and Exchange
                  Commission on March 30, 2005)



                                       7
<PAGE>

21.0              Subsidiaries (Incorporated by reference to Exhibit 21.0 of the
                  Registrant's  Form 10-KSB for the fiscal  year ended  December
                  31,  2004,   and  filed  with  the   Securities  and  Exchange
                  Commission on March 30, 2005)

23.1              Consent of Hein & Associates LLP (Incorporated by reference to
                  Exhibit  23.1 of the  Registrant's  Form 10-KSB for the fiscal
                  year ended  December 31, 2004,  and filed with the  Securities
                  and Exchange Commission on March 30, 2005)

*31.1             Certification  of Chief Executive  Officer required by Section
                  302 of the Sarbanes-Oxley Act of 2002

*31.2             Certification  of Chief Financial  Officer required by Section
                  302 of the Sarbanes-Oxley Act of 2002

*32.1             Certification  required by Section  906 of the  Sarbanes-Oxley
                  Act of 2002

*32.2             Certification  required by Section  906 of the  Sarbanes-Oxley
                  Act of 2002


-----------------------------
 * Filed herewith.









                                       8
<PAGE>

                                   SIGNATURES


         In  accordance  with  Section  13 or 15(d)  of the  Exchange  Act,  the
registrant  caused  this  report to be signed on its behalf by the  undersigned,
thereunto duly authorized.





Date:  July 6, 2005                          NATURAL GAS SERVICES GROUP, INC.



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




                                             By: /s/ Earl R.Wait
                                                --------------------------------
                                                Earl R. Wait, Chief Financial
                                                Officer










                                       9
<PAGE>

                                                             EXHIBIT INDEX


         The  following  is a list of all  exhibits  filed as part of this  Form
10-KSB/A:

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


2.1               Purchase and Sale Agreement by and between Hy-Bon  Engineering
                  Company, Inc. and NGE Leasing, Inc. (Incorporated by reference
                  to Exhibit 2.1 of the Registrant's  Current Report on Form 8-K
                  dated  February  28,  2003 and filed with the  Securities  and
                  Exchange Commission on March 6, 2003)

3.1               Articles  of  Incorporation,   as  amended   (Incorporated  by
                  reference to Exhibit 3.1 of the 10QSB filed and dated November
                  10, 2004)

3.2               Bylaws  (Incorporated  by  reference  to  Exhibit  3.4  of the
                  Registrant's   Registration   Statement  on  Form  SB-2,   No.
                  333-88314)

4.1               Form of warrant  certificate  (Incorporated  by  reference  to
                  Exhibit 4.1 of the Registrant's Registration Statement on Form
                  SB-2, No. 333-88314)

4.2               Form of warrant agent agreement  (Incorporated by reference to
                  Exhibit 4.2 of the Registrant's Registration Statement on Form
                  SB-2, No. 333-88314)

4.3               Form  of  lock-up  agreement  (Incorporated  by  reference  to
                  Exhibit 4.3 of the Registrant's Registration Statement on Form
                  SB-2, No. 333-88314)

4.4               Form of  representative's  option for the  purchase  of common
                  stock  (Incorporated  by  reference  to  Exhibit  4.4  of  the
                  Registrant's   Registration   Statement  on  Form  SB-2,   No.
                  333-88314)

4.5               Form of  representative's  option for the purchase of warrants
                  (Incorporated  by reference to Exhibit 4.5 of the Registrant's
                  Registration Statement on Form SB-2, No. 333-88314)

4.6               Stockholders  Agreement,  dated  January 3, 2005 among Paul D.
                  Hensley,  Tony Vohjesus,  Jim Hazlett and Natural Gas Services
                  Group,  Inc.  (Incorporated by reference to Exhibit 4.3 of the
                  Registrant's From 8-K Report,  dated January 3, 2005, as filed
                  with the  Securities  and  Exchange  Commission  on January 7,
                  2005)

                  Executive  Compensation Plans and Arrangements (Exhibits 10.1,
                  10.24, 10.25 and 10.26)


<PAGE>

10.1              1998 Stock Option Plan  (Incorporated  by reference to Exhibit
                  10.1 of the Registrant's  Registration Statement on Form SB-2,
                  No. 333-88314)

10.2              Asset Purchase  Agreement,  dated January 1, 2001, between the
                  Registrant and Great Lakes Compression,  Inc. (Incorporated by
                  reference  to Exhibit  10.2 of the  Registrant's  Registration
                  Statement on Form SB-2, No. 333-88314)

10.3              Exhibits  3(c)(1),  3(c)(2),   3(c)(3),   3(c)(4),   13(d)(1),
                  13(d)(2)  and  13(d)(3)  to Asset  Purchase  Agreement,  dated
                  January  1,  2001,  between  the  Registrant  and Great  Lakes
                  Compression,  Inc. (Incorporated by reference to Exhibit 10.14
                  of the Registrant's  Registration  Statement on Form SB-2, No.
                  333-88314)

10.4              Amendment to Guaranty  Agreement  between Natural Gas Services
                  Group, Inc. and Dominion Michigan  Production  Services,  Inc.
                  (Incorporated by reference to Exhibit 10.3 of the Registrant's
                  Registration Statement on Form SB-2, No. 333-88314)

10.5              Form of Series A 10% Subordinated  Notes due December 31, 2006
                  (Incorporated by reference to Exhibit 10.8 of the Registrant's
                  Registration Statement on Form SB-2, No. 333-88314)

10.6              Form  of   Five-Year   Warrants  to  Purchase   Common   Stock
                  (Incorporated by reference to Exhibit 10.9 of the Registrant's
                  Registration Statement on Form SB-2, No. 333-88314)

10.7              Warrants issued to Berry-Shino Securities,  Inc. (Incorporated
                  by reference to Exhibit 10.10 of the Registrant's Registration
                  Statement on Form SB-2, No. 333-88314)

10.8              Warrants   issued   to   Neidiger,    Tucker,   Bruner,   Inc.
                  (Incorporated   by   reference   to   Exhibit   10.11  of  the
                  Registrant's   Registration   Statement  on  Form  SB-2,   No.
                  333-88314)

10.9              Form of  warrant  issued in March 2001 for  guaranteeing  debt
                  (Incorporated   by   reference   to   Exhibit   10.12  of  the
                  Registrant's   Registration   Statement  on  Form  SB-2,   No.
                  333-88314)

10.10             Form of  warrant  issued in April 2002 for  guaranteeing  debt
                  (Incorporated   by   reference   to   Exhibit   10.13  of  the
                  Registrant's   Registration   Statement  on  Form  SB-2,   No.
                  333-88314)

10.11             Articles of Organization of Hy-Bon Rotary Compression, L.L.C.,
                  dated April 17, 2000  (Incorporated  by  reference  to Exhibit
                  10.18 of the Registrant's Registration Statement on Form SB-2,
                  No. 333-88314)



<PAGE>

10.12             Regulations of Hy-Bon Rotary Compression, L.L.C. (Incorporated
                  by reference to Exhibit 10.19 of the Registrant's Registration
                  Statement on Form SB-2, No. 333-88314)

10.13             First  Amended  and  Restated  Loan   Agreement   between  the
                  Registrant  and  Western   National  Bank   (Incorporated   by
                  reference to Exhibit 10.1 of the  Registrant's  Current Report
                  on  Form  8-K,  dated  March  27,  2003  and  filed  with  the
                  Securities and Exchange Commission on April 14, 2003)

10.14             Form of Termination of Employment Agreement Letter relating to
                  the  Employment  Agreement  of  Alan  Kurus  (Incorporated  by
                  reference to Exhibit 10.25 of the  Registrant's  Annual Report
                  on Form 10-KSB for the fiscal year ended December 31, 2002)

10.15             Form of Termination of Employment Agreement Letter relating to
                  the  Employment  Agreement  of Wayne Vinson  (Incorporated  by
                  reference to Exhibit 10.26 of the  Registrant's  Annual Report
                  on Form 10-KSB for the fiscal year ended December 31, 2002)

10.16             Form of Termination of Employment Agreement Letter relating to
                  the  Employment   Agreement  of  Earl  Wait  (Incorporated  by
                  reference to Exhibit 10.27 of the  Registrant's  Annual Report
                  on Form 10-KSB for the fiscal year ended December 31, 2002)

10.17             Triple Net Lease  Agreement,  dated June 1, 2003,  between NGE
                  Leasing, Inc. and Steven J. & Katherina L. Winer (Incorporated
                  by  reference  to  Exhibit  10.17 of the  Registrant's  Annual
                  Report on Form 10-KSB for the fiscal year ended  December  31,
                  2003)

10.18             Lease  Agreement,  dated June 19,  2003,  between NGE Leasing,
                  Inc. and Wise Commercial Properties (Incorporated by reference
                  to Exhibit  10.18 of the  Registrant's  Annual  Report on Form
                  10-KSB for the fiscal year ended December 31, 2003)

10.19             Lease Agreement,  dated March 1, 2004,  between the Registrant
                  and the City of Midland,  Texas  (Incorporated by reference to
                  Exhibit 10.19 of the  Registrant's  Form 10-QSB for the fiscal
                  quarter ended June 30, 2004)

10.20             Second Amended and Restated Loan Agreement,  dated November 3,
                  2003,   between  the  Registrant  and  Western  National  Bank
                  (Incorporated   by   reference   to   Exhibit   10.20  of  the
                  Registrant's Form 10-QSB for the fiscal quarter ended June 30,
                  2004)

10.21             Securities  Purchase  Agreement,  dated July 20, 2004, between
                  the Registrant and CBarney Investments,  Ltd. (Incorporated by
                  reference to Exhibit 4.1 of the Registrant's Current Report on
                  Form 8-K dated July 20, 2004 and filed with the Securities and
                  Exchange Commission on July 27, 2004)



<PAGE>

10.22             Stock Purchase Agreement, dated October 18, 2004, by and among
                  the  Registrant,  Screw  Compression  Systems,  Inc.,  Paul D.
                  Hensley,  Jim  Hazlett  and  Tony  Vohjesus  (Incorporated  by
                  reference to Exhibit 4.1 of the Registrant's Current Report on
                  Form 8-K dated October 18, 2004 and filed with the  Securities
                  and Exchange Commission on October 21, 2004)

10.23             Fourth  Amended and Restated Loan Agreement  (Incorporated  by
                  reference to Exhibit 10.1 of the  Registrant's  Current Report
                  on Form 8-K, dated March 14, 2005 as filed with the Securities
                  and Exchange Commission on March 18, 2005)

10.24             Employment  Agreement  between Paul D. Hensley and Natural Gas
                  Services  Group,  Inc.  (Incorporated  by reference to Exhibit
                  10.1 of the  Registrants  Form 8-K  Report,  dated  January 3,
                  2005, as filed with the Securities and Exchange  Commission on
                  January 7, 2005)

10.25             Employment Agreement between William R. Larkin and Natural Gas
                  Services  Group,  Inc.  (Incorporated  by reference to Exhibit
                  10.25 of the  Registrant's  Form  10-KSB for the  fiscal  year
                  ended  December 31, 2004,  and filed with the  Securities  and
                  Exchange Commission on March 30, 2005)

10.26             Promissory  Note,  dated  January  3,  2005,  in the  original
                  principal amount of $2,100,000.00 made by Natural Gas Services
                  Group,  Inc.  payable  to Paul  D.  Hensley  (Incorporated  by
                  reference to Exhibit 10.26 of the Registrant's Form 10-KSB for
                  the fiscal year ended  December 31,  2004,  and filed with the
                  Securities and Exchange Commission on March 30, 2005)

14.0              Code of Ethics  (Incorporated  by reference to Exhibit 14.0 of
                  the  Registrant's  Form  10-KSB  for  the  fiscal  year  ended
                  December 31, 2004,  and filed with the Securities and Exchange
                  Commission on March 30, 2005)

21.0              Subsidiaries (Incorporated by reference to Exhibit 21.0 of the
                  Registrant's  Form 10-KSB for the fiscal  year ended  December
                  31,  2004,   and  filed  with  the   Securities  and  Exchange
                  Commission on March 30, 2005)

23.1              Consent of Hein & Associates LLP (Incorporated by reference to
                  Exhibit  23.1 of the  Registrant's  Form 10-KSB for the fiscal
                  year ended  December 31, 2004,  and filed with the  Securities
                  and Exchange Commission on March 30, 2005)

*31.1             Certification  of Chief Executive  Officer required by Section
                  302 of the Sarbanes-Oxley Act of 2002



<PAGE>

*31.2             Certification  of Chief Financial  Officer required by Section
                  302 of the Sarbanes-Oxley Act of 2002

*32.1             Certification  required by Section  906 of the  Sarbanes-Oxley
                  Act of 2002

*32.2             Certification  required by Section  906 of the  Sarbanes-Oxley
                  Act of 2002


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 * Filed herewith.