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


                                    FORM 8-K


                 CURRENT REPORT PURSUANT TO SECTION 13 OR 15(d)
                     OF THE SECURITIES EXCHANGE ACT OF 1934


          Date of Report (Date of earliest event reported): May 9, 2006


                        NATURAL GAS SERVICES GROUP, INC.
             (Exact Name of Registrant as Specified in Its Charter)


             Colorado                        1-31398              75-2811855
  (State or other jurisdiction          (Commission File        (IRS Employer
of Incorporation or organization)            Number)         Identification No.)


2911 South County Road 1260 Midland, Texas                           79706
 (Address of Principal Executive Offices)                         (Zip Code)

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


                                 Not Applicable
          (Former name or former address, if changed since last report)


Check  the  appropriate  box  below  if the  Form  8-K  filing  is  intended  to
simultaneously  satisfy the filing obligation of the registrant under any of the
following provisions:

[_]  Written  communications  pursuant to Rule 425 under the  Securities Act (17
     CFR 230.425)

[_]  Soliciting  material pursuant to Rule 14a-12 under the Exchange Act (17 CFR
     240.14a-12)

[_]  Pre-commencement   communications  pursuant  to  Rule  14d-2(b)  under  the
     Exchange Act (17 CFR 240.14d-2(b))

[_}  Pre-commencement   communications  pursuant  to  Rule  13e-4(c)  under  the
     Exchange  Act  (17  CFR  240.13e-4(c))



Item 1.01   Entry into a Material Definitive Agreement

     On December 18, 1998, the Board of Directors of Natural Gas Services Group,
Inc. adopted the 1998 Stock Option Plan (the "1998 Plan"), and directed that the
1998 Plan be submitted to the  shareholders  for approval.  The 1998 Plan became
effective when it received such approval on December 18, 1998.

     On May 9, 2006, the Compensation  Committee of the Board of Directors voted
to amend the 1998 Plan and on that same date,  the Board of  Directors  directed
that such  amendments be submitted for the approval of  shareholders at the 2006
Annual  Meeting of  Shareholders.  Such  amendments  will become  effective if a
majority of the votes cast are in favor of the proposal.  If the  amendments are
not approved, the 1998 Plan will remain in force as originally adopted.

     The proposed  amendments change the 1998 Plan in five principal respects as
follows:

     1. The number of shares of common stock  authorized  for issuance under the
1998 Plan will be increased from 150,000 to 550,000 shares of common stock.

     2. The Compensation Committee will have a longer period during which it may
grant options. The 1998 Plan, prior to amendment,  provided that no grants could
be made after  December 17, 2008. As provided in the  amendment,  options can be
granted until March 1, 2016.

     3. The 1998 Plan,  prior to amendment,  provided that the exercise price of
incentive stock options granted to employees who do not own more than 10% of our
common  stock would be not less than 140% of the fair market  value per share of
our common stock on the date of grant. The amendment  provides that the exercise
price of incentive  stock options  granted to such employees under the 1998 Plan
will be not less than 100% of the fair market  value of our common  stock on the
date of grant.

     4. The 1998 Plan,  prior to amendment,  contained a provision  allowing the
Compensation Committee to increase,  without shareholder approval, the number of
shares of stock subject to the 1998 Plan from 150,000 shares to 400,000  shares.
This provision of the 1998 Plan is eliminated in the amendment.

     5. The  1998  Plan,  prior to  amendment,  provided  that the  Compensation
Committee,  in its sole discretion,  could provide an optionee with the right to
exchange, in a cashless transaction, all or part of a stock option for shares of
our  common  stock  on  terms  and  conditions  determined  by the  Compensation
Committee.  This provision of the 1998 Plan could potentially  result in adverse
accounting  consequences  under FASB  Statement No.  123(R),  which was recently
adopted by Natural Gas Services  Group.  Therefore,  this  provision of the 1998
Plan is eliminated in the amendment.

     The  purposes  of the  1998  Plan,  which  are  unchanged  by the  proposed
amendment,  are to attract and retain the best available personnel for positions
of substantial responsibility,  to provide additional incentive to employees and
consultants and to promote the success of our business.


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Summary Description of the 1998 Plan

     The  following  summary of the 1998 Plan,  as amended,  is qualified in its
entirety  by  reference  to the  text of the 1998  Plan,  as  amended,  which is
attached  as  Exhibit  10.1.  The 1998  Plan has  been and will  continue  to be
administered by the  Compensation  Committee of the Board of Directors.  Options
granted under the 1998 Plan may be either  "incentive  stock options" within the
meaning of Section 422 of the  Internal  Revenue  Code of 1986,  as amended (the
"Code") or options which do not constitute  incentive options.  The Compensation
Committee has full and final  authority,  in its discretion,  to grant incentive
stock options or nonstatutory stock options,  to select the persons who would be
granted stock options and determine the number of shares subject to each option,
the duration and exercise  period of each option and the terms and conditions of
each option granted.

     The major provisions of the 1998 Plan as amended are as follows:

          Eligibility.  The Compensation  Committee is authorized to grant stock
     options to any person  selected by the  Compensation  Committee,  including
     employees,  officers who are also directors of Natural Gas Services  Group,
     directors  who  are  not  employees  of  Natural  Gas  Services  Group  and
     consultants.  Incentive  stock  options may be granted only to employees of
     Natural Gas Services Group.

          Option  Price.  The option  exercise  price for shares of common stock
     issued  upon  exercise of an option is such price as is  determined  by the
     Compensation  Committee.  However,  for incentive  stock options granted to
     employees  the option  price will be not less than 100% of the fair  market
     value of the  Company's  common  stock on the date the  option is  granted,
     except that if an incentive stock option is granted to an employee who owns
     more than 10% of Natural Gas'  outstanding  common stock,  the option price
     will be not less than 110% of the fair market  value of the common stock on
     the date of grant.  Fair market  value for purposes of the 1998 Plan is the
     closing  price  of the  common  stock as  reported  on the  American  Stock
     Exchange on the relevant date.

          Duration of Options.  Each stock  option  will  terminate  on the date
     fixed by the Compensation Committee, which shall be not more than ten years
     after the date of grant.  However, in the case of an incentive stock option
     granted to an employee  who, at the time the option is granted,  owns stock
     representing more than 10% of the outstanding stock of Natural Gas Services
     Group,  the term of the option will be five years from the date of grant or
     such shorter time as may be provided in the stock option agreement.

          Exercise  Period.  In the  case  of  incentive  stock  options,  if an
     optionee's  employment  is  terminated  for any  reason,  except  death  or
     disability,  the  optionee  has three months in which to exercise an option
     (but only to the extent exercisable on the date of termination)  unless the
     option by its terms  expires  earlier.  If the  employment  of the optionee
     terminates by reason of total and permanent  disability,  the option may be
     exercised  during  the period of twelve  months  following  termination  of
     employment.  If an optionee  dies while an employee or within  three months


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     from the date of termination,  the right to exercise shall terminate twelve
     months from the date of death. The options  terminate  immediately prior to
     the  dissolution or liquidation of Natural Gas Services  Group,  unless the
     Compensation Committee gives each optionee the right to exercise his option
     as to all or any part of the  option,  including  shares  as to  which  the
     option would not otherwise be  exercisable.  If Natural Gas Services  Group
     sells all or substantially all of its assets or merges with or into another
     entity in a transaction  in which it is not the  survivor,  options will be
     assumed  or an  equivalent  option  will be  substituted  by the  successor
     corporation, unless the Compensation Committee determines that the optionee
     has the right to  exercise  the option as to all of the  shares,  including
     shares as to which the  option  would not  otherwise  be  exercisable.  The
     Compensation  Committee  has the right to alter the terms of any  option at
     grant or while outstanding pursuant to the terms of the 1998 Plan.

          Payment. Payment for stock purchased on the exercise of a stock option
     must be made  in full at the  time  the  stock  option  is  exercised.  The
     Compensation  Committee  may,  in its  discretion,  permit  payment for the
     exercise  price to be made in cash,  check,  other  shares of common  stock
     having a fair market value on the date of exercise  equal to the  aggregate
     exercise  price of the shares as to which the option is  exercised,  or any
     combination  of such methods of payment,  or such other  consideration  and
     method  of  payment  for the  issuance  of shares  as  permitted  under the
     Colorado Business Corporation Act.

          Shares  That May Be Issued  under the 1998 Plan.  A maximum of 550,000
     shares of Natural Gas' common stock, as may be adjusted as described below,
     may be issued upon exercise of stock  options  granted under the 1998 Plan.
     This number  includes  the number of shares of Natural  Gas'  common  stock
     originally  authorized in 1998 (150,000 shares).  Consequently,  a total of
     400,000  additional  shares will be  authorized  pursuant  to the  proposed
     amendment.  The 400,000 additional shares available represent approximately
     3.35% of Natural  Gas' common  stock  issued and  outstanding  on April 26,
     2006. As of May 15, 2005,  140,500 shares of common stock have already been
     issued or are subject to currently outstanding stock options, leaving 9,500
     shares  of  common  stock  available  from the  150,000  shares  originally
     authorized.  The number of shares  available under the 1998 Plan is subject
     to   adjustment  in  the  event  of  any  stock  split,   stock   dividend,
     recapitalization,  spin-off or other  similar  action.  If any stock option
     terminates or is canceled for any reason  without  having been exercised in
     full,  the  shares  of stock not  issued  will then  become  available  for
     additional grants of options.

     Termination  of and  Amendments to the 1998 Plan The Board of Directors may
terminate  or amend the 1998 Plan from time to time in any manner  permitted  by
applicable  laws and  regulations,  except that no  additional  shares of common
stock of Natural Gas  Services  Group may be  allocated  to the 1998 Plan and no
change in the class of employees  eligible to receive incentive stock options or
any other  material  amendment to the 1998 Plan may be made without the approval
of the shareholders.


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Item 9.01.  Financial Statements and Exhibits.

     (c)  Exhibits

     The exhibits  listed below are furnished as exhibits to this Current Report
on Form 8-K.

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

             10.1          Natural Gas Services  Group,  Inc.  1998 Stock Option
                           Plan, as amended on May 9, 2006

             10.2          Form  of  Nonstatutory  Stock  Option  Agreement  for
                           non-employee directors

             10.3          Form  of  Incentive   Stock  Option   Agreement   for
                           employees

             10.4         Form  of  Nonstatutory  Stock  Option  Agreement  for
                           employees and consultants















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                                   SIGNATURES

     Pursuant to the  requirements  of the Securities  Exchange Act of 1934, the
Registrant  has duly  caused  this  report  to be  signed  on its  behalf by the
undersigned hereunto duly authorized.

                                                NATURAL GAS SERVICES GROUP, INC.


                                             By: /s/ Stephen C. Taylor
                                                --------------------------------
                                                Stephen C. Taylor, Chairman
                                                of the Board, President and
                                                Chief Executive Officer


Dated:  May 15, 2006















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                                  EXHIBIT INDEX



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

   10.1             Natural Gas Services Group,  Inc. 1998 Stock Option Plan, as
                    amended on May 9, 2006

   10.2             Form of Nonstatutory Stock Option Agreement for non-employee
                    directors

   10.3             Form of Incentive Stock Option Agreement for employees

   10.4             Form of  Nonstatutory  Stock Option  Agreement for employees
                    and consultants