NATURAL GAS SERVICES GROUP, INC. 1998 STOCK OPTION PLAN

1.            Purposes of this Plan.   The purposes of this 1998 Stock Option Plan 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 the Company’s business. Options granted hereunder may be either “incentive stock options,” as defined in Section 422 of the Internal Revenue Code of 1986, as amended, or “nonstatutory stock options,” at the discretion of the Board and as reflected in the terms of the written stock option agreement.

2.            Definitions.    As used herein, the following definitions shall apply:

           a.           “Board” shall mean the Committee, if one has been appointed, or the Board of Directors of the Company if no Committee is appointed.

           b.           “Code” shall mean the Internal Revenue Code of 1986, as amended.

           c.           “Common Stock” shall mean the $0.01 par value common stock of the Company.

           d.           “Company” shall mean Natural Gas Services Group, Inc., a Colorado corporation.

           e.           “Committee” shall mean the Committee appointed by the Board in accordance with paragraph (a) of Section 4 of this Plan, if one is appointed, or the Board if no committee is appointed.

           f.           “Consultant” shall mean any person who is engaged by the Company or by any Parent or Subsidiary to render consulting services and is compensated for such consulting services, but does not include a director of the Company who is compensated for services as a director only with the payment of a director’s fee by the Company.

           g           “Continuous Status as an Employee” shall mean the absence of any interruption or termination of service as an Employee. Continuous Status as an Employee shall not be considered interrupted in the case of sick leave, military leave, or any other leave of absence approved by the Board, provided that such leave is for a period of not more than 90 days or reemployment upon the expiration of such leave is guaranteed by contract or statute.

           h.           “Employee” shall mean any person, including officers and directors, employed by the Company or by any Parent or Subsidiary. The payment of a director’s fee by the Company shall not be sufficient to constitute “employment” by the Company.

     i.           “Incentive Stock Option” shall mean an Option which is intended to qualify as an incentive stock option within the meaning of Section 422 of the Code and which shall be clearly identified as such in the written Stock Option Agreement provided by the Company to each Optionee granted an Incentive Stock Option under this Plan.

           j.           “Non-Employee Director” shall mean a director who:

           (i)           Is not currently an officer (as defined in Section 16a-1(1) of the Securities Exchange Act of 1934, as amended) of the Company or of a Parent or Subsidiary or otherwise currently employed by the Company or by a Parent or Subsidiary.

           (ii)           Does not receive compensation, either directly or indirectly, from the Company or from a Parent or Subsidiary, for services rendered as a Consultant or in any capacity other than as a director, except for an amount that does not exceed the dollar amount for which disclosure would be required pursuant to Item 404(a) of Regulation S-K adopted by the United States Securities and Exchange Commission.

           (iii)           Does not possess an interest in any other transaction for which disclosure would be required pursuant to Item 404(a) of Regulation S-K adopted by the United States Securities and Exchange Commission.

           k.           “Nonstatutory Stock Option” shall mean an Option granted under this Plan which does not qualify as an Incentive Stock Option and which shall be clearly identified as such in the written Stock Option Agreement provided by the Company to each Optionee granted a Nonstatutory Stock Option under this Plan. To the extent that the aggregate fair market value of Optioned Stock to which Incentive Stock Options granted under Options to an Employee are exercisable for the first time during any calendar year (under this Plan and all plans of the Company or any Parent or Subsidiary) exceeds $100,000, such Options shall be treated as Nonstatutory Stock Options under this Plan. The aggregate fair market value of the Optioned Stock shall be determined as of the date of grant of each Option and the determination of which Incentive Stock Options shall be treated as qualified incentive stock options under Section 422 of the Code and which Incentive Stock Options exercisable for the first time in a particular year in excess of the $100,000 limitation shall be treated as Nonstatutory Stock Options shall be determined based on the order in which such Options were granted in accordance with Section 422(d) of the Code.

           l.           “Option” shall mean an Incentive Stock Option, a Nonstatutory Stock Option or both as identified in a written Stock Option Agreement representing such stock option granted pursuant to this Plan.

           m.           “Optioned Stock” shall mean the Common Stock subject to an Option.

           n.           “Optionee” shall mean an Employee or other person who is granted an option.

           o.           “Parent” shall mean a “parent corporation” of the Company, whether now or hereafter existing, as defined in Section 424(e) of the Code.

           p.            “Plan” shall mean this 1998 Stock Option Plan.

           q.           “Share” shall mean a share of the Common Stock of the Company, as adjusted in accordance with Section 11 of this Plan.

           r.           “Stock Option Agreement” shall mean the agreement to be entered into between the Company and each Optionee which shall set forth the terms and conditions of each Option granted to each Optionee, including the number of Shares underlying such Option and the exercise price of each Option granted to such Optionee under such agreement.

           s.           “Subsidiary” shall mean a “subsidiary corporation” of the Company, whether now or hereafter existing, as defined in Section 424(f) of the Code.

3.             Stock Subject to this Plan.    Subject to the provisions of Section 11 of this Plan, the maximum aggregate number of Shares which may be optioned and sold under this Plan is 750,000 shares of Common Stock. The Shares may be authorized, but unissued, or reacquired Common Stock. If an Option should expire or become unexercisable for any reason without having been exercised in full, the unpurchased Shares which were subject thereto shall, unless this Plan shall have been terminated, become available for future grant under this Plan.

4.            Administration of this Plan.

           a.            Procedure.   This Plan shall be administered by the Board or a Committee appointed by the Board consisting of two or more Non-Employee Directors to administer this Plan on behalf of the Board, subject to such terms and conditions as the Board may prescribe.

           (i)           Once appointed, the Committee shall continue to serve until otherwise directed by the Board (which for purposes of this paragraph (a)(i) of this Section 4 shall be the Board of Directors of the Company). From time to time the Board may increase the size of the Committee and appoint additional members thereof, remove members (with or without cause) and appoint new members in substitution therefor, fill vacancies however caused, or remove all members of the Committee and thereafter directly administer this Plan.

           (ii)           Members of the Board who are granted, or have been granted, Options may vote on any matters affecting the administration of this Plan or the grant of any Options pursuant to this Plan.

           b.            Powers of the Board.   Subject to the provisions of this Plan, the Board shall have the authority, in its discretion:

           (i)           To grant Incentive Stock Options, in accordance with Section 422 of the Code, and Nonstatutory Stock Options or both as provided and identified in a separate written Stock Option Agreement to each Optionee granted such Option or Options under this Plan; provided however, that in no event shall an Incentive Stock Option and a Nonstatutory Stock Option granted to any Optionee under a single Stock Option Agreement be subject to a “tandem” exercise arrangement such that the exercise of one such Option affects the Optionee’s right to exercise the other Option granted under such Stock Option Agreement;

           (ii)          To determine, upon review of relevant information and in accordance with Section 8(b) of this Plan, the fair market value of the Common Stock;

           (iii)         To determine the exercise price per Share of Options to be granted, which exercise price shall be determined in accordance with Section 8(a) of this Plan;

           (iv)          To determine the Employees or other persons to whom, and the time or times at which, Options shall be granted and the number of Shares to be represented by each Option;

           (v)           To interpret this Plan;

           (vi)          To prescribe, amend and rescind rules and regulations relating to this Plan;

           (vii)         To determine the terms and provisions of each Option granted (which need not be identical) and, with the consent of the holder thereof, modify or amend each Option;

           (viii)        To accelerate or defer (with the consent of the Optionee) the exercise date of any Option, consistent with the provisions of Section 7 of this Plan;

           (ix)          To authorize any person to execute on behalf of the Company any instrument required to effectuate the grant of an Option previously granted by the Board; and

           (x)           To make all other determinations deemed necessary or advisable for the administration of this Plan.

c.            Effect of Board’s Decision.   All decisions, determinations and interpretations of the Board shall be final and binding on all Optionees and any other permissible holders of any Options granted under this Plan.

5.             Eligibility.

           a.            Persons Eligible.   Options may be granted to any person selected by the Board. Incentive Stock Options may be granted only to Employees.  An Employee, who is also a director of the Company, its Parent or a Subsidiary, shall be treated as an Employee for purposes of this Section 5.  An Employee or other person who has been granted an Option may, if he is otherwise eligible, be granted an additional Option or Options.

           b.            No Effect on Relationship.   This Plan shall not confer upon any Optionee any right with respect to continuation of employment or other relationship with the Company nor shall it interfere in any way with his right or the Company’s right to terminate his employment or other relationship at any time.

6.              Term of Pl