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                                                                   Exhibit 10.6

                              EMPLOYMENT AGREEMENT


     THIS EMPLOYMENT AGREEMENT, made and entered into as of January 1, 1999 (the
"EFFECTIVE Date"), by and between Lexicon Genetics Incorporated, a Delaware
corporation (hereafter "COMPANY"), and Randall Riggs (hereafter "EXECUTIVE"), an
individual and resident of Montgomery County, Texas.

                              W I T N E S S E T H:

     WHEREAS, Company wishes to secure the services of the Executive subject to
the terms and conditions hereafter set forth; and

     WHEREAS, the Executive is willing to enter into this Agreement upon the
terms and conditions hereafter set forth,

     NOW, THEREFORE, in consideration of the mutual promises and agreements set
forth herein, the parties hereto agree as follows:

     1. EMPLOYMENT. During the Employment Period (as defined in Section 4
hereof), the Company shall employ Executive, and Executive shall serve, as Vice
President - Business Development. Executive's principal place of employment
shall be at the Company's principal corporate offices in The Woodlands, Texas,
or at such other location for the Company's principal corporate offices during
the Employment Period.

     2. DUTIES AND RESPONSIBILITIES OF EXECUTIVE.

          (a) During the Employment Period, Executive shall devote his services
     full time to the business of the Company and its Affiliates (as defined
     below), and perform the duties and responsibilities assigned to him by the
     Chief Executive Officer ("CEO") or Board of Directors (the "BOARD") of the
     Company to the best of his ability and with reasonable diligence. Executive
     agrees to cooperate fully with the Board, CEO and other executive officers
     of the Company, and not to engage in any activity which conflicts with or
     interferes with the performance of his duties hereunder. During the
     Employment Period, Executive shall devote his best efforts and skills to
     the business and interests of Company, do his utmost to further enhance and
     develop Company's best interests and welfare, and endeavor to improve his
     ability and knowledge of Company's business, in an effort to increase the
     value of his services for the mutual benefit of the parties hereto. During
     the Employment Period, it shall not be a violation of this Agreement for
     Executive to (1) serve on corporate, civic, or charitable boards or
     committees (except for boards or committees of a Competing Business (as
     defined in Section 11)), (2) deliver lectures, fulfill teaching or speaking


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          engagements, or (3) manage personal investments, so long as such
          activities do not materially interfere with performance of Executive's
          responsibilities under this Agreement.

               For purposes of this Agreement, "AFFILIATE" means any entity
          which owns or controls, is owned or controlled by, or is under common
          ownership or control with, the Company.

               (b) Executive represents and covenants to Company that he is not
          subject or a party to any employment agreement, noncompetition
          covenant, nondisclosure agreement, or any similar agreement, covenant,
          understanding, or restriction that would prohibit Executive from
          executing this Agreement and fully performing his duties and
          responsibilities hereunder, or would in any manner, directly or
          indirectly, limit or affect the duties and responsibilities that may
          now or in the future be assigned to Executive hereunder.

          3. COMPENSATION. During the Employment Period, the Company shall pay
     to Executive an annual base salary of $160,000, in consideration for his
     services under this Agreement, payable on a pro rata basis in not less than
     monthly installments, in conformity with the Company's customary payroll
     practices for executive salaries. Executive's base salary shall be subject
     to review at least annually, and such salary may be adjusted, depending
     upon the performance of the Company and Executive, upon the recommendation
     of the Compensation Committee of the Board (the "COMPENSATION COMMITTEE").
     All salary and any other compensation payments hereunder shall be subject
     to all applicable payroll and other taxes.

          4. TERM OF EMPLOYMENT. Executive's initial term of employment with the
     Company under this Agreement shall be for the two-year period beginning on
     the Effective Date and ending at midnight (CST) on December 31, 2000,
     unless Notice of Termination pursuant to Section 7 is given by either the
     Company or Executive to the other party. The Company and Executive shall
     each have the right to give Notice of Termination at will, with or without
     cause, at any time, subject to the terms and conditions of this Agreement
     regarding the rights and duties of the parties upon termination of
     employment. The term of employment hereunder ending on December 31, 2000,
     shall be referred to herein as the "INITIAL TERM OF EMPLOYMENT." On
     December 31, 2000 and on December 31st of each succeeding year (each such
     date being referred to as a "Renewal Date"), this Agreement shall
     automatically renew and extend for a period of one (1) additional year (a
     "RENEWAL TERM") unless written notice of nonrenewal is delivered from one
     party to the other at least sixty (60) days prior to the relevant Renewal
     Date or, alternatively, the parties may mutually agree to voluntarily enter
     into a new employment agreement at any time. The period from the Effective
     Date through the date of Executive's termination of employment at any time
     for whatever reason shall be referred to herein as the "EMPLOYMENT PERIOD."

          5. BENEFITS. Subject to the terms and conditions of this Agreement,
     during the Employment Period, Executive shall be entitled to the
     following:

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               (a) REIMBURSEMENT OF BUSINESS EXPENSES. The Company shall pay or
          reimburse Executive for all reasonable travel, entertainment and other
          expenses paid or incurred by Executive in performing his business
          obligations hereunder. Executive shall provide substantiating
          documentation for expense reimbursement requests as reasonably
          required by the Company.

               (b) BENEFITS. Executive shall be entitled to and shall receive
          all other benefits and conditions of employment available generally to
          executives of the Company pursuant to Company plans and programs,
          including, but not limited to, group health insurance benefits, dental
          benefits, life insurance benefits, disability benefits, and pension
          and retirement benefits. The Company shall not be obligated to
          institute, maintain, or refrain from changing, amending, or
          discontinuing, any such employee benefit program or plan, so long as
          such actions are similarly applicable to covered executives generally.

               Notwithstanding the previous paragraph, Company shall provide
          Executive with long-term disability ("LTD") insurance coverage, at no
          cost to Executive, that provides income replacement benefits to
          Executive, if he should incur a long-term disability covered under
          such policy, in an amount at least equal to 60% of his base salary at
          the time of such disability, which benefits shall begin after a
          waiting period that does not exceed six months. The income replacement
          benefits described in the previous sentence shall remain payable at
          least until Executive attains the age of 65 provided that he remains
          unable to perform the essential functions of his occupation during
          such period. To the extent that the Company's LTD policy which covers
          employees generally does not provide sufficient coverage to Executive,
          as described in the previous sentence, Company agrees to purchase a
          supplemental LTD policy for Executive from a reputable insurer and to
          pay the premiums on behalf of Executive during the Employment Period.

               Notwithstanding the first paragraph of this Section 3(b), the
          Company shall pay for term life insurance coverage on Executive's
          life, with the beneficiary(ies) thereof designated by Executive, with
          a death benefit in an amount not less than twice Executive's base
          salary (pursuant to Section 3(a)) as such base salary is set on each
          January 1 during the Employment Period. Upon request, Executive agrees
          to take any physical exams, and to provide such information, which are
          reasonably necessary or appropriate to secure or maintain such term
          life insurance coverage.

               (c) PAID VACATION. Executive shall be entitled to a paid annual
          vacation of three (3) weeks. Vacation time may be accumulated and
          carried over by Executive into any subsequent year(s); provided,
          however, Executive shall not be permitted to accumulate more than six
          weeks of accrued and unused vacation. In addition, the Executive shall
          be allowed up to five (5) days each year to attend professional
          continuing education meetings or seminars; provided, that attendance
          at such meetings or

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          seminars shall be planned for minimum interference with the Company's
          business.

          6. RIGHTS AND PAYMENTS UPON TERMINATION. The Executive's right to
     compensation and benefits for periods after the date on which his
     employment with the Company and its Affiliates (as defined in Section 2)
     terminates for whatever reason (the "TERMINATION DATE") shall be determined
     in accordance with this Section 6.

               (a) ACCRUED SALARY AND VACATION PAYMENTS. Executive shall be
          entitled to the following payments under this Section 6(a), in
          addition to any payments or benefits to which the Executive is
          entitled under the terms of any employee benefit plan or the following
          provisions of this Section 6:

                    (1) his accrued but unpaid salary through his Termination
               Date; and

                    (2) his accrued but unpaid vacation pay for the period
               ending on his Termination Date in accordance with Section 5(c)
               above.

               (b) SEVERANCE PAYMENTS.

                    (1) At any time prior to a Change in Control (as defined
               below), in the event that (A) Executive's employment hereunder is
               terminated by the Company at any time for any reason except (i)
               for Cause (as defined below) or (ii) due to Executive's death or
               Disability (as defined below), or (B) Executive terminates his
               own employment hereunder for Good Reason (as defined below),
               then, in either such event, Executive shall be entitled to
               receive, and the Company shall be obligated to pay, Executive's
               base salary under Section 3(a) (without regard to any bonuses or
               extraordinary compensation) then being paid to him on the
               Termination Date as salary continuation (pursuant to the
               Company's normal payroll procedures) for a period equal to six
               (6) consecutive months following the Termination Date; provided
               that if such termination occurs within 120 days following a
               reduction in Executive's base salary, such salary continuation
               payments shall be made in an amount equal to Executive's base
               salary prior to such reduction. In the event of Executive's death
               during such salary continuation period, the Company shall pay the
               sum of the present value of all remaining payments (using a 5%
               discount rate) in a single payment to the Executive's estate
               within 60 days of his death. Such severance payments shall be
               subject to Sections 10 and 11 hereof.

                    Prior to a Change in Control, in the event that Executive's
               employment is terminated through notice of nonrenewal as of the
               end of the Initial Term of Employment (pursuant to Section 4) or
               any one-year Renewal Term, Executive shall

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          not be entitled to receive any severance payments pursuant to the
          first paragraph of this Section 6(a); provided, however, Executive
          shall be entitled to receive a severance payment equal to $13,000 per
          month for each month following his Termination Date, not to exceed six
          months, that Executive is (A) not in violation of the confidential
          information, non-competition and other covenants of Sections 10 and 11
          hereof and (B) not employed by another employer, as determined by the
          Company.

               (2) At any time after a Change in Control (as defined below), in
          the event that (A) Executive's employment hereunder is terminated by
          the Company at any time for any reason except (i) for Cause (as
          defined below) or (ii) due to Executive's death or Disability (as
          defined below), or (B) Executive terminates his own employment
          hereunder for Good Reason (as defined below in this paragraph), then,
          in either such event, Executive shall be entitled to receive, and the
          Company shall be obligated to pay, Executive's base salary under
          Section 3(a) (without regard to any bonuses or extraordinary
          compensation except as provided below in this paragraph) then being
          paid to him on the Termination Date as salary continuation (pursuant
          to the Company's normal payroll procedures) for a period equal to
          twelve (12) consecutive months following the Termination Date, plus an
          additional single sum payment equal to one-half of Executive's target
          bonus (pursuant to Section 3(b)) for the Bonus Year that contains the
          Termination Date which bonus shall be payable within 30 days from the
          Termination Date; provided that if such termination occurs within 120
          days following a reduction in Executive's base salary, such salary
          continuation payments shall be made in an amount equal to Executive's
          base salary prior to such reduction. In the event of Executive's death
          during such salary continuation period, the Company shall pay the sum
          of the present value of all remaining payments in a single payment
          (using a 5% discount rate) to the Executive's estate within 60 days of
          his death.

               After a Change in Control, in the event that the Company
          terminates Executive's employment through notice of nonrenewal as of
          the end of the Initial Term of Employment (pursuant to Section 4) or
          any one-year Renewal Term, Executive shall be entitled to receive, and
          the Company shall be obligated to pay, Executive's base salary under
          Section 3(a) (without regard to any bonuses or extraordinary
          compensation) then being paid to him on the Termination Date as salary
          continuation (pursuant to the Company's normal payroll procedures) for
          a period of six (6) consecutive months following the Termination Date.

               (3) Except as otherwise specifically provided in this Section
          6(b), severance payments shall be in addition to, and shall not reduce
          or offset, any other payments that are due to Executive from the
          Company (or any other source) or under any other

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          agreements, except that severance payments hereunder shall offset any
          severance benefits otherwise due to Executive under any severance pay
          plan or program maintained by the Company that covers its employees
          generally. The provisions of this Section 6(b) shall supersede any
          conflicting provisions of this Agreement but shall not be construed to
          curtail, offset or limit Executive's rights to any other payments,
          whether contingent upon a Change in Control (as defined below) or
          otherwise, under this Agreement or any other agreement, contract, plan
          or other source of payment except as specifically provided herein.

               (4) A "CHANGE IN CONTROL" of the Company shall be deemed to have
          occurred if any of the following shall have taken place: (A) any
          "person" (as such term is used in Sections 13(d) and 14(d)(2) of the
          Securities Exchange Act of 1934 (the "Exchange Act")) other than
          Gordon Cain is or becomes the "beneficial owner" (as defined in Rule
          13d-3 under the Exchange Act, or any successor provisions thereto),
          directly or indirectly, of securities of the Company representing
          thirty-five percent (35%) or more of the combined voting power of the
          Company's then-outstanding voting securities; (B) the approval by the
          stockholders of the Company of a reorganization, merger, or
          consolidation, in each case with respect to which persons who were
          stockholders of the Company immediately prior to such reorganization,
          merger, or consolidation do not, immediately thereafter, own or
          control more than fifty percent (50%) of the combined voting power
          entitled to vote generally in the election of directors of the
          reorganized, merged or consolidated Company's then outstanding
          securities in substantially the same proportion as their ownership of
          the Company's outstanding voting securities prior to such
          reorganization, merger or consolidation; (C) a liquidation or
          dissolution of the Company or the sale of all or substantially all of
          the Company's assets; (D) in the event any person is elected by the
          stockholders of the Company to the Board who has not been nominated
          for election by a majority of the Board or any duly appointed
          committee thereof; or (E) following the election or removal of
          directors, a majority of the Board consists of individuals who were
          not members of the Board two (2) years before such election or
          removal, unless the election of each director who is not a director at
          the beginning of such two-year period has been approved in advance by
          directors representing at least a majority of the directors then in
          office who were directors at the beginning of the two-year period. The
          Board, in its discretion, may deem any other corporate event affecting
          the Company to be a "Change in Control" hereunder.

               (5) "DISABILITY" means a permanent and total disability which
          entitles Executive to disability income payments under the Company's
          long-term disability plan or policy as then in effect which covers
          Executive pursuant to Section 5(b). If

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          Executive is not covered under the Company's long-term disability plan
          or policy at such time for whatever reason or under a supplemental LTD
          policy provided by the Company, then the term "Disability" hereunder
          shall mean a "permanent and total disability" as defined in Section
          22(e)(3) of the Code and, in this case, the existence of any such
          Disability shall be certified by a physician acceptable to both the
          Company and Executive. In the event that the parties are not able to
          agree on the choice of a physician, each shall select a physician who,
          in turn, shall select a third physician to render such certification.
          All costs relating to the determination of whether Executive has
          incurred a Disability shall be paid by the Company.

               (6) "CODE" means the Internal Revenue Code of 1986, as amended.
          References in this Agreement to any Section of the Code shall include
          any successor provisions of the Code or its successor.

               (7) "CAUSE" means a termination of employment directly resulting
          from (1) the Executive having engaged in intentional misconduct
          causing a material violation by the Company of any state or federal
          laws, (2) the Executive having engaged in a theft of corporate funds
          or corporate assets or in a material act of fraud upon the Company,
          (3) an act of personal dishonesty taken by the Executive that was
          intended to result in substantial personal enrichment of the Executive
          at the expense of the Company, (4) Executive's final conviction (or
          the entry of a plea of nolo contendere or equivalent plea) in a court
          of competent jurisdiction of a felony, or (5) a breach by the
          Executive during the Employment Period of the provisions of Sections
          9, 10, and 11 hereof, if such breach results in a material injury to
          the Company. For purposes of this definition of "Cause", the term
          "Company" shall mean the Company or any of its Affiliates (as defined
          in Section 2).

               (8) "GOOD REASON" means the occurrence of any of the following
          events without Executive's express written consent:

                   (A) Before a Change in Control (as defined in Section 6(b)),
               (i) a five percent (5%) or greater reduction in Executive's
               annual base salary unless any such greater pay cut is applied
               across the board to the other senior officers of the Company
               except the CEO, or (ii) after a Change in Control, any reduction
               in Executive's base salary, provided that, in either event,
               Executive specifically terminates his employment for Good Reason
               hereunder within 120 days from the date that he has actual notice
               of such reduction; or

                   (B) Before or after a Change in Control, any breach by the
               Company of any material provision of this Agreement, provided
               that Executive

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          specifically terminates his employment for Good Reason
          hereunder within 120 days from the date that he has actual notice of
          such material breach; or

               (C) Only following a Change in Control (as defined in Section
          6(b)), any of the following events will constitute Good Reason,
          provided that Executive specifically terminates his employment for
          Good Reason hereunder within 12 months following his receipt of actual
          notice of an event listed below:

                    (i) the failure by the Company or its successor to expressly
               assume and agree to continue and perform this Agreement in the
               same manner and to the same extent that the Company would be
               required to perform if such Change in Control had not occurred;

                    (ii) Executive's duties or responsibilities for the Company
               or its successor are materially reduced; or

                    (iii) the Company or its successor fails to continue in
               effect any pension, medical, health-and-accident, life insurance,
               or disability income plan or program in which Executive was
               participating at the time of the Change in Control (or plans
               providing Executive with substantially similar benefits), or the
               taking of any action by the Company or its successor that would
               adversely affect Executive's participation in or materially
               reduce his benefits under any such plan that was enjoyed by him
               immediately prior to the Change in Control.

          7. NOTICE OF TERMINATION. Any termination by the Company or the
     Executive shall be communicated by Notice of Termination to the other party
     hereto. For purposes of this Agreement, the term "NOTICE OF TERMINATION"
     means a written notice that indicates the specific termination provision of
     this Agreement relied upon and sets forth in reasonable detail the facts
     and circumstances claimed to provide a basis for termination of the
     Executive's employment under the provision so indicated.

          8. NO MITIGATION REQUIRED. Executive shall not be required to mitigate
     the amount of any payment provided for under this Agreement by seeking
     other employment or in any other manner.

          9. CONFLICTS OF INTEREST.

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               (a) In keeping with his fiduciary duties to Company, Executive
          hereby agrees that he shall not become involved in a conflict of
          interest, or upon discovery thereof, allow such a conflict to continue
          at any time during the Employment Period. Moreover, Executive agrees
          that he shall immediately disclose to the Board any facts which might
          involve a conflict of interest that has not been approved by the
          Board.

               (b) Executive and Company recognize and acknowledge that it is
          not possible to provide an exhaustive list of actions or interests
          which may constitute a "conflict of interest." Moreover, Company and
          Executive recognize there are many borderline situations. In some
          instances, full disclosure of facts by the Executive to the Board may
          be all that is necessary to enable Company to protect its interests.
          In others, if no improper motivation appears to exist and Company's
          interests have not demonstrably suffered, prompt elimination of the
          outside interest may suffice. In other serious instances, it may be
          necessary for the Company to terminate Executive's employment for
          Cause (as defined in Section 6(b)). The Board reserves the right to
          take such action as, in its good faith judgment, will resolve the
          conflict of interest.

               (c) Executive hereby agrees that any direct or indirect interest
          in, connection with, or benefit from any outside activities,
          particularly commercial activities, which interest might adversely
          affect the Company or any of its Affiliates (as defined in Section 2),
          involves a possible conflict of interest. Circumstances in which a
          conflict of interest on the part of Executive would or might arise,
          and which must be reported immediately to the Board, include, but are
          not limited to, any of the following:

                    (1) Ownership by the Executive and his immediate family
               members of more than a two percent (2%) interest, on an
               aggregated basis, in any lender, supplier, contractor, customer
               or other entity with which Company or any of its Affiliates does
               business;

                    (2) Misuse of information, property or facilities to which
               Executive has access in a manner which is demonstrably and
               materially injurious to the interests of Company or any of its
               Affiliates, including its business, reputation or goodwill; or

                    (3) Materially trading in products or services connected
               with products or services designed or marketed by or for the
               Company or any of its Affiliates.

          10. CONFIDENTIAL INFORMATION.

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               (a) NON-DISCLOSURE OBLIGATION OF EXECUTIVE. For purposes of this
          Section 10, all references to Company shall mean and include its
          Affiliates (as defined in Section 2). Executive hereby acknowledges,
          understands and agrees that all Confidential Information, as defined
          in Section 10(b), whether developed by Executive or others employed by
          or in any way associated with Executive or Company, is the exclusive
          and confidential property of Company and shall be regarded, treated
          and protected as such in accordance with this Agreement. Executive
          acknowledges that all such Confidential Information is in the nature
          of a trade secret. Failure to mark any writing confidential shall not
          affect the confidential nature of such writing or the information
          contained therein.

               (b) DEFINITION OF CONFIDENTIAL INFORMATION. The term
          "CONFIDENTIAL INFORMATION" shall mean information, whether or not
          originated by Executive, which is used in Company's business and (1)
          is proprietary to, about or created by Company; (2) gives Company some
          competitive business advantage or the opportunity of obtaining such
          advantage, or the disclosure of which could be detrimental to the
          interests of Company; (3) is designated as Confidential Information by
          Company, known by the Executive to be considered confidential by
          Company, or from all the relevant circumstances considered
          confidential by Company, or from all the relevant circumstances should
          reasonably be assumed by Executive to be confidential and proprietary
          to Company; or (4) is not generally known by non-Company personnel.
          Such Confidential Information includes, but is not limited to, the
          following types of information and other information of a similar
          nature (whether or not reduced to writing or designated as
          confidential):

                    (1) Work product resulting from or related to the research,
               development or production of the programs of the Company
               including, without limitation, OmniBank(TM), homologous
               recombination, DNA sequencing, phenotypic analysis, drug target
               validation and drug discovery;

                    (2) Internal Company personnel and financial information,
               vendor names and other vendor information (including vendor
               characteristics, services and agreements), purchasing and
               internal cost information, internal service and operational
               manuals, and the manner and methods of conducting Company's
               business;

                    (3) Marketing, partnering and business and development
               plans, price and cost data, price and fee amounts, pricing and
               billing policies, quoting procedures, marketing techniques and
               methods of obtaining business, forecasts and forecast assumptions
               and volumes, and future plans and potential strategies of the
               Company which have been or are being discussed; and

                    (4) Business acquisition and other business opportunities.


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               (c) EXCLUSIONS FROM CONFIDENTIAL INFORMATION. The term
          "CONFIDENTIAL INFORMATION" shall not include information publicly
          known other than as a result of a disclosure by Executive in breach of
          Section 10(a), and the general skills and experience gained during
          Executive's work with the Company which Executive could reasonably
          have been expected to acquire in similar work with another company.

               (d) COVENANTS OF EXECUTIVE. As a consequence of Executive's
          acquisition or anticipated acquisition of Confidential Information,
          Executive shall occupy a position of trust and confidence with respect
          to Company's affairs and business. In view of the foregoing and of the
          consideration to be provided to Executive, Executive agrees that it is
          reasonable and necessary that Executive make the following covenants:

                    (1) At any time during the Employment Period and within ten
               (10) years after the Employment Period, Executive shall not
               disclose Confidential Information to any person or entity, either
               inside or outside of Company, other than as necessary in carrying
               out duties on behalf of Company, without obtaining Company's
               prior written consent (unless such disclosure is compelled
               pursuant to court order or subpoena, and at which time Executive
               gives notice of such proceedings to Company), and Executive will
               take all reasonable precautions to prevent inadvertent disclosure
               of such Confidential Information. This prohibition against
               Executive's disclosure of Confidential Information includes, but
               is not limited to, disclosing the fact that any similarity exists
               between the Confidential Information and information
               independently developed by another person or entity, and
               Executive understands that such similarity does not excuse
               Executive from abiding by his covenants or other obligations
               under this Agreement.

                    (2) At any time during or after the Employment Period,
               Executive shall not use, copy or transfer Confidential
               Information other than as necessary in carrying out his duties on
               behalf of Company, without first obtaining Company's prior
               written consent, and will take all reasonable precautions to
               prevent inadvertent use, copying or transfer of such Confidential
               Information. This prohibition against Executive's use, copying,
               or transfer of Confidential Information includes, but is not
               limited to, selling, licensing or otherwise exploiting, directly
               or indirectly, any products or services (including databases,
               written documents and software in any form) which embody or are
               derived from Confidential Information, or exercising judgment in
               performing analyses based upon knowledge of Confidential
               Information.

               (e) RETURN OF CONFIDENTIAL MATERIAL. Executive shall promptly
          turn over to the person designated by the Board or CEO all originals
          and copies of materials containing Confidential Information in the
          Executive's possession, custody, or control upon request or upon
          termination of Executive's employment with Company. Executive agrees
          to attend a termination interview with the person or persons
          designated by the Board or CEO in the

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         Company's offices for a reasonable time period. The purposes of the
         termination interview shall be (1) to confirm turnover of all
         Confidential Information, (2) discuss any questions Executive may have
         about his continuing obligations under this Agreement, (3) answer
         questions related to his duties and on-going projects to allow a
         temporary or permanent successor to obtain a better understanding of
         the employment position, (4) confirm the number of any outstanding
         stock options, or other long-term incentive awards, and their vested
         percentages and other terms and conditions, and (5) any other topics
         relating to the business affairs of Company or its Affiliates as
         determined by the Company.

                  (f) INVENTIONS. Any and all inventions, products, discoveries,
         improvements, copyrightable or patentable works or products,
         trademarks, service marks, ideas, processes, formulae, methods,
         designs, techniques and trade secrets (collectively hereinafter
         referred to as "INVENTIONS") made, developed, conceived or resulting
         from work performed by Executive (alone or in conjunction with others,
         during regular hours of work or otherwise) while he is employed by
         Company and which may be directly or indirectly useful in, or related
         to, the business of Company (including, without limitation, research
         and development activities of Company), or which are made using any
         equipment, facilities, Confidential Information, materials, labor,
         money, time or other resources of Company, shall be promptly disclosed
         by Executive to the person or persons designated by the Board or CEO,
         shall be deemed Confidential Information for purposes of this
         Agreement, and shall be Company's exclusive property. Executive shall,
         upon Company's reasonable request during or after the Employment
         Period, execute any documents and perform all such acts and things
         which are necessary or advisable in the opinion of Company to cause
         issuance of patents to, or otherwise obtain recorded protection of
         right to intellectual property for, Company with respect to Inventions
         that are to be Company's exclusive property under this Section 10, or
         to transfer to and vest in Company full and exclusive right, title and
         interest in and to such Inventions; provided, however, that the expense
         of securing any such protection of right to Inventions shall be borne
         by Company. In addition, during or after the Employment Period,
         Executive shall, at Company's expense, reasonably assist the Company in
         any reasonable and proper manner in enforcing any Inventions which are
         to be or become Company's exclusive property hereunder against
         infringement by others. Executive shall keep confidential and will hold
         for Company's sole use and benefit any Invention that is to be
         Company's exclusive property under this Section 10 for which full
         recorded protection of right has not been or cannot be obtained.

                  (g) PROPERTY RIGHTS. In keeping with his fiduciary duties to
         Company, Executive hereby covenants and agrees that during his
         Employment Period, and for a period of three (3) months following his
         Termination Date, Executive shall promptly disclose in writing to
         Company any and all Inventions, which are conceived, developed, made or
         acquired by Executive, either individually or jointly with others, and
         which directly relate to the business, products or services of Company.
         In consideration for his employment hereunder, Executive

                                                                Initials:_______

                                                                Initials:_______

                                       12
<PAGE>   13


     hereby specifically sells, assigns and transfers to Company all of his
     worldwide right, title and interest in and to all such Inventions.

          If during the Employment Period, Executive creates any original work
     of authorship or other property fixed in any tangible medium of expression
     which (1) is the subject matter of copyright (including computer programs)
     and (2) directly relates to Company's present or planned business,
     products, or services, whether such property is created solely by Executive
     or jointly with others, such property shall be deemed a work for hire, with
     the copyright automatically vesting in Company. To the extent that any such
     writing or other property is determined not to be a work for hire for
     whatever reason, Executive hereby consents and agrees to the unconditional
     waiver of "moral rights" in such writing or other property, and to assign
     to Company all of his right, title and interest, including copyright, in
     such writing or other property.

          Executive hereby agrees to (1) assist Company or its nominee at all
     times in the protection of any property that is subject to this Section 10,
     (2) not to disclose any such property to others without the written consent
     of Company or its nominee, except as required by his employment hereunder,
     and (3) at the request of Company, to execute such assignments,
     certificates or other interests as Company or its nominee may from time to
     time deem desirable to evidence, establish, maintain, perfect, protect or
     enforce its rights, title or interests in or to any such property.

         (h) EMPLOYEE PROPRIETARY INFORMATION AGREEMENT. The provisions of this
     Section 10 shall not supersede the Employee Proprietary Information
     Agreement (the "Proprietary Agreement") between Employee and the Company
     (or any other agreement of similar intent) which shall remain in full force
     and effect and, moreover, this Agreement, the Proprietary Agreement and any
     such other similar agreement between the parties shall be construed and
     applied as being mutually consistent to the full extent possible.

         (i) REMEDIES. In the event of a breach or threatened breach of any of
     the provisions of this Section 10, Company shall be entitled to an
     injunction ordering the return of all such Confidential Information and
     Inventions, and restraining Executive from using or disclosing, for his
     benefit or the benefit of others, in whole or in part, any Confidential
     Information or Inventions. Executive further agrees that any breach or
     threatened breach of any of the provisions of this Section 10 would cause
     irreparable injury to Company, for which it would have no adequate remedy
     at law. Nothing herein shall be construed as prohibiting Company from
     pursuing any other remedies available to it for any such breach or
     threatened breach, including the recovery of damages.

     11. AGREEMENT NOT TO COMPETE. All references in this Section 11 to
"COMPANY" shall mean and include its Affiliates (as defined in Section 2).

                                                                Initials:_______

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                                       13
<PAGE>   14


              (a) PROHIBITED EXECUTIVE ACTIVITIES. Executive agrees that
         except in the ordinary course and scope of his employment hereunder
         during the Employment Period, Executive shall not while employed by
         Company and, except as specifically provided below in this Section
         11(a), for a period of six (6) months following his Termination Date,
         within the continental United States:

                         (1) Directly or indirectly, engage or invest in, own,
                    manage, operate, control or participate in the ownership,
                    management, operation or control of, be employed by,
                    associated or in any manner connected with, or render
                    services or advice to, any Competing Business (as defined
                    below); provided, however, Executive may invest in the
                    securities of any enterprise with the power to vote up to
                    two percent (2%) of the capital stock of such enterprise
                    (but without otherwise participating in the activities of
                    such enterprise) if such securities are listed on any
                    national or regional securities exchange or have been
                    registered under Section 12(g) of the Securities Exchange
                    Act of 1934;

                         (2) Directly or indirectly, either as principal, agent,
                    independent contractor, consultant, director, officer,
                    employee, employer, advisor (whether paid or unpaid),
                    stockholder, partner or in any other individual or
                    representative capacity whatsoever, either for his own
                    benefit or for the benefit of any other person or entity,
                    solicit, divert or take away, any customers, clients, or
                    business acquisition or other business opportunities of
                    Company; or

                         (3) Directly or indirectly, either as principal, agent,
                    independent contractor, consultant, director, officer,
                    employee, advisor (whether paid or unpaid), stockholder,
                    partner or in any other individual or representative
                    capacity whatsoever, either for his own benefit or for the
                    benefit of any other person or entity, either (A) hire,
                    attempt to hire, contact or solicit with respect to hiring
                    any employee of Company, (B) induce or otherwise counsel,
                    advise or encourage any employee of Company to leave the
                    employment of Company, or (C) induce any distributor,
                    representative or agent of Company to terminate or modify
                    its relationship with Company.

                         In the event that Executive's Termination Date occurs
                    after a Change in Control (as defined in Section 6(b)), then
                    notwithstanding any provisions of this Section 11 to the
                    contrary, all of the non-compete restrictions set forth in
                    this Section 11 shall not apply to, or be enforced against,
                    Executive if his employment with the Company or its
                    successor is terminated (1) by Executive for Good Reason (as
                    defined in Section 6(b)), (2) by the Company or its
                    successor without Cause (as defined in Section 6(b), or (3)
                    upon notice of nonrenewal pursuant to Section 4. Therefore,
                    following a Change in Control, in the event that Executive
                    terminates his

                                                                Initials:_______

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                                       14
<PAGE>   15


         employment for Good Reason or upon notice of nonrenewal, or the Company
         or its successor terminates Executive's employment without Cause or
         upon nonrenewal, Executive shall not be subject to the provisions of
         Section 11.

                  "COMPETING BUSINESS" means any individual, business, firm,
         company, partnership, joint venture, organization, or other entity
         whose products or services compete, in whole or in part, at any time
         during the Employment Period with the products or services (or planned
         products and services) of Company including, without limitation,
         genomics research, development and products including, without
         limitation, OmniBank(TM), homologous recombination, DNA sequencing,
         phenotypic analysis, drug validation and drug discovery.

         (b) ESSENTIAL NATURE OF NON-COMPETE OBLIGATION. It is acknowledged,
understood and agreed by and between the parties hereto that the covenants made
by Executive in this Section 11 are essential elements of this Agreement and
that, but for the agreement of the Executive to comply with such covenants,
Company would not have entered into this Agreement.

         (c) NECESSITY AND REASONABLENESS OF NON-COMPETE OBLIGATION. Executive
hereby specifically acknowledges and agrees that:

                  (1) Company has expended and will continue to expend
         substantial time, money and effort in developing its business;

                  (2) Executive will, in the course of his employment, be
         personally entrusted with and exposed to Confidential Information (as
         defined in Section 10);

                  (3) Company, during the Employment Period and thereafter, will
         be engaged in its highly competitive business in which many firms,
         including Company, compete;

                  (4) Executive could, after having access to Company's
         financial records, contracts, and other Confidential Information and
         know-how and, after receiving training by and experience with the
         Company, become a competitor;

                  (5) Company will suffer great loss and irreparable harm if
         Executive terminates his employment and enters, directly or indirectly,
         into competition with Company;

                  (6) The temporal and other restrictions contained in this
         Section 11 are in all respects reasonable and necessary to protect the
         business goodwill, trade secrets, prospects and other reasonable
         business interests of Company;

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                                       15
<PAGE>   16


                          (7) The enforcement of this Agreement in general, and
                  of this Section 11 in particular, will not work an undue or
                  unfair hardship on Executive or otherwise be oppressive to
                  him; it being specifically acknowledged and agreed by
                  Executive that he has activities and other business interests
                  and opportunities which will provide him adequate means of
                  support if the provisions of this Section 11 are enforced
                  after the Termination Date; and

                          (8) the enforcement of this Agreement in general, and
                  of this Section 11 in particular, will neither deprive the
                  public of needed goods or services nor otherwise be injurious
                  to the public.

                  (d) JUDICIAL MODIFICATION. Executive agrees that if an
         arbitrator (pursuant to Section 21) or a court of competent
         jurisdiction determines that the length of time or any other
         restriction, or portion thereof, set forth in this Section 11 is overly
         restrictive and unenforceable, the arbitrator or court shall reduce or
         modify such restrictions to those which it deems reasonable and
         enforceable under the circumstances, and as so reduced or modified, the
         parties hereto agree that the restrictions of this Section 11 shall
         remain in full force and effect. Executive further agrees that if an
         arbitrator or court of competent jurisdiction determines that any
         provision of this Section 11 is invalid or against public policy, the
         remaining provisions of this Section 11 and the remainder of this
         Agreement shall not be affected thereby, and shall remain in full force
         and effect.

         12. REMEDIES. In the event of any pending, threatened or actual breach
of any of the covenants or provisions of Section 9, 10, or 11, it is understood
and agreed by Executive that the remedy at law for a breach of any of the
covenants or provisions of these Sections may be inadequate and, therefore,
Company shall be entitled to a restraining order or injunctive relief from any
court of competent jurisdiction, in addition to any other remedies at law and in
equity. In the event that Company seeks to obtain a restraining order or
injunctive relief, Executive hereby agrees that Company shall not be required to
post any bond in connection therewith. Should a court of competent jurisdiction
or an arbitrator (pursuant to Section 21) declare any provision of Section 9,
10, or 11 to be unenforceable due to an unreasonable restriction of duration or
geographical area, or for any other reason, such court or arbitrator is hereby
granted the consent of each of the Executive and Company to reform such
provision and/or to grant the Company any relief, at law or in equity,
reasonably necessary to protect the reasonable business interests of Company or
any of its affiliated entities. Executive hereby acknowledges and agrees that
all of the covenants and other provisions of Sections 9, 10, and 11 are
reasonable and necessary for the protection of the Company's reasonable business
interests. Executive hereby agrees that if the Company prevails in any action,
suit or proceeding with respect to any matter arising out of or in connection
with Section 9, 10, or 11, Company shall be entitled to all equitable and legal
remedies, including, but not limited to, injunctive relief and compensatory
damages.

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                                       16
<PAGE>   17


         13. DEFENSE OF CLAIMS. Executive agrees that, during the Employment
Period and for a period of two (2) years after his Termination Date, upon
request from the Company, he will cooperate with the Company and its Affiliates
in the defense of any claims or actions that may be made by or against the
Company or any of its Affiliates that affect his prior areas of responsibility,
except if Executive's reasonable interests are adverse to the Company or
Affiliates in such claim or action. To the extent travel is required to comply
with the requirements of this Section 13, the Company shall, to the extent
possible, provide Executive with notice at least 10 days prior to the date on
which such travel would be required. The Company agrees to promptly pay or
reimburse Executive upon demand for all of his reasonable travel and other
direct expenses incurred, or to be reasonably incurred, to comply with his
obligations under this Section 13.

         14. DETERMINATIONS BY THE BOARD OF DIRECTORS.

                  (a) TERMINATION OF EMPLOYMENT. Prior to a Change in Control
         (as defined in Section 6(b)), any question as to whether and when there
         has been a termination of Executive's employment, the cause of such
         termination, and the Termination Date, shall be determined by the
         Compensation Committee in its discretion exercised in good faith.

                  (b) COMPENSATION. Prior to a Change in Control (as defined in
         Section 6(b)), any question regarding salary, bonus and other
         compensation payable to Executive pursuant to this Agreement shall be
         determined by the Compensation Committee in its discretion exercised in
         good faith.

         15. WITHHOLDINGS; RIGHT OF OFFSET. Company may withhold and deduct from
any benefits and payments made or to be made pursuant to this Agreement (a) all
federal, state, local and other taxes as may be required pursuant to any law or
governmental regulation or ruling, (b) all other employee deductions made with
respect to Company's employees generally, and (c) any advances made to Executive
and owed to Company.

         16. NONALIENATION. The right to receive payments under this Agreement
shall not be subject in any manner to anticipation, alienation, sale, transfer,
assignment, pledge or encumbrance by Executive, his dependents or beneficiaries,
or to any other person who is or may become entitled to receive such payments
hereunder. The right to receive payments hereunder shall not be subject to or
liable for the debts, contracts, liabilities, engagements or torts of any person
who is or may become entitled to receive such payments, nor may the same be
subject to attachment or seizure by any creditor of such person under any
circumstances, and any such attempted attachment or seizure shall be void and of
no force and effect.


         17. INCOMPETENT OR MINOR PAYEES. Should the Board determine that any
person to whom any payment is payable under this Agreement has been determined
to be legally incompetent or is

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                                       17
<PAGE>   18


a minor, any payment due hereunder may, notwithstanding any other provision of
this Agreement to the contrary, be made in any one or more of the following
ways: (a) directly to such minor or person; (b) to the legal guardian or other
duly appointed personal representative of the person or estate of such minor or
person; or (c) to such adult or adults as have, in the good faith knowledge of
the Board, assumed custody and support of such minor or person; and any payment
so made shall constitute full and complete discharge of any liability under this
Agreement in respect to the amount paid.

         18. SEVERABILITY. It is the desire of the parties hereto that this
Agreement be enforced to the maximum extent permitted by law, and should any
provision contained herein be held unenforceable by a court of competent
jurisdiction or arbitrator (pursuant to Section 21), the parties hereby agree
and consent that such provision shall be reformed to create a valid and
enforceable provision to the maximum extent permitted by law; provided, however,
if such provision cannot be reformed, it shall be deemed ineffective and deleted
herefrom without affecting any other provision of this Agreement.

         19. TITLE AND HEADINGS; CONSTRUCTION. Titles and headings to Sections
hereof are for the purpose of reference only and shall in no way limit, define
or otherwise affect the provisions hereof. Any and all Exhibits referred to in
this Agreement are, by such reference, incorporated herein and made a part
hereof for all purposes. The words "herein", "hereof", "hereunder" and other
compounds of the word "here" shall refer to the entire Agreement and not to any
particular provision hereof.

         20. CHOICE OF LAW. THIS AGREEMENT SHALL BE GOVERNED BY AND CONSTRUED IN
ACCORDANCE WITH THE LAWS OF THE STATE OF TEXAS, WITHOUT REGARD TO THE PRINCIPLES
OF CONFLICTS OF LAW.

         21. ARBITRATION.






                                                                Initials:_______

                                                                Initials:_______


                                       18
<PAGE>   19


                  (a) ARBITRABLE MATTERS. If any dispute or controversy arises
         between Executive and the Company relating to (1) this Agreement in any
         way or arising out of the parties' respective rights or obligations
         under this Agreement or (2) the employment of Executive or the
         termination of such employment, then either party may submit the
         dispute or controversy to arbitration under the then-current Commercial
         Arbitration Rules of the American Arbitration Association (AAA) (the
         "RULES"); provided, however, the Company shall retain its rights to
         seek a restraining order or injunctive relief pursuant to Section 12.
         Any arbitration hereunder shall be conducted before a single arbitrator
         unless the parties mutually agree that the arbitration shall be
         conducted before a panel of three arbitrators. The arbitrator shall be
         selected through mutual agreement of the parties, if possible. If the
         parties fail to reach agreement upon appointment of the arbitrator
         within twenty (20) days following receipt by one party of the other
         party's notice of desire to arbitrate, then within five (5) days
         following the end of such 20-day period, each party shall select one
         arbitrator who, in turn, shall within five (5) days select a third
         arbitrator who shall be the single arbitrator hereunder. The site for
         any arbitration hereunder shall be in Harris County or Montgomery
         County, Texas, unless otherwise mutually agreed by the parties, and the
         parties hereby waive any objection that the forum is inconvenient.

                  (b) SUBMISSION TO ARBITRATION. The party submitting any matter
         to arbitration shall do so in accordance with the Rules. Notice to the
         other party shall state the question or questions to be submitted for
         decision or award by arbitration. Notwithstanding any provision of this
         Section 21, Executive shall be entitled to seek specific performance of
         the Executive's right to be paid during the pendency of any dispute or
         controversy arising under this Agreement. In order to prevent
         irreparable harm, the arbitrator may grant temporary or permanent
         injunctive or other equitable relief for the protection of property
         rights.

                  (c) ARBITRATION PROCEDURES. The arbitrator shall set the date,
         time and place for each hearing, and shall give the parties advance
         written notice in accordance with the Rules. Any party may be
         represented by counsel or other authorized representative at any
         hearing. The arbitration shall be governed by the Federal Arbitration
         Act, 9 U.S.C. Sections 1 et. seq. (or its successor). The arbitrator
         shall apply the substantive law (and the law of remedies, if
         applicable) of the State of Texas to the claims asserted to the extent
         that the arbitrator determines that federal law is not controlling.

                  (d) COMPLIANCE WITH AWARD.

                           (1) Any award of an arbitrator shall be final and
                  binding upon the parties to such arbitration, and each party
                  shall immediately make such changes in its conduct or provide
                  such monetary payment or other relief as such award requires.
                  The parties agree that the award of the arbitrator shall be
                  final and binding and shall be subject only to the judicial
                  review permitted by the Federal Arbitration Act.

                                                                Initials:_______

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                                       19
<PAGE>   20


                           (2) The parties hereto agree that the arbitration
                  award may be entered with any court having jurisdiction and
                  the award may then be enforced as between the parties, without
                  further evidentiary proceedings, the same as if entered by the
                  court at the conclusion of a judicial proceeding in which no
                  appeal was taken. The Company and the Executive hereby agree
                  that a judgment upon any award rendered by an arbitrator may
                  be enforced in other jurisdictions by suit on the judgment or
                  in any other manner provided by law.

                  (e) COSTS AND EXPENSES. Each party shall pay any monetary
         amount required by the arbitrator's award, and the fees, costs and
         expenses for its own counsel, witnesses and exhibits, unless otherwise
         determined by the arbitrator in the award. The compensation and costs
         and expenses assessed by the arbitrator and the AAA shall be split
         evenly between the parties unless otherwise determined by the
         arbitrator in the award. If court proceedings to stay litigation or
         compel arbitration are necessary, the party who opposes such
         proceedings to stay litigation or compel arbitration, if such party is
         unsuccessful, shall pay all associated costs, expenses, and attorney's
         fees which are reasonably incurred by the other party as determined by
         the arbitrator.

         22. BINDING EFFECT; THIRD PARTY BENEFICIARIES. This Agreement shall be
binding upon and inure to the benefit of the parties hereto, and to their
respective heirs, executors, personal representatives, successors and permitted
assigns hereunder, but otherwise this Agreement shall not be for the benefit of
any third parties.

         23. ENTIRE AGREEMENT AND AMENDMENT. This Agreement contains the entire
agreement of the parties with respect to Executive's employment and the other
matters covered herein; moreover, this Agreement supersedes all prior and
contemporaneous agreements and understandings, oral or written, between the
parties hereto concerning the subject matter hereof. This Agreement may be
amended, waived or terminated only by a written instrument executed by both
parties hereto.

         24. SURVIVAL OF CERTAIN PROVISIONS. Wherever appropriate to the
intention of the parties hereto, the respective rights and obligations of said
parties, including, but not limited to, the rights and obligations set forth in
Sections 6 through 14 and 21 hereof, shall survive any termination or expiration
of this Agreement.

         25. WAIVER OF BREACH. No waiver by either party hereto of a breach of
any provision of this Agreement by any other party, or of compliance with any
condition or provision of this Agreement to be performed by such other party,
will operate or be construed as a waiver of any subsequent breach by such other
party or any similar or dissimilar provision or condition at the same or any
subsequent time. The failure of either party hereto to take any action by reason
of any breach will not deprive such party of the right to take action at any
time while such breach continues.

                                                                Initials:_______

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                                       20
<PAGE>   21


         26. SUCCESSORS AND ASSIGNS. This Agreement shall be binding upon and
inure to the benefit of Company and its Affiliates (as defined in Section 2),
and upon any successor to the Company following a Change in Control (as defined
in Section 6(b)); provided, however, any such assignment by the Company shall
not relieve Company of its obligations hereunder. Any reference herein to
"Company" shall mean the Company as first written above, as well as any
successor or successors thereto.

         This Agreement is personal to Executive, and Executive may not assign,
delegate or otherwise transfer all or any of his rights, duties or obligations
hereunder without the consent of the Board. Any attempt by the Executive to
assign, delegate or otherwise transfer this Agreement, any portion hereof, or
his rights, duties or obligations hereunder without the prior approval of the
Board shall be deemed void and of no force and effect.

         27. NOTICES. Notices provided for in this Agreement shall be in writing
and shall be deemed to have been duly received (a) when delivered in person or
sent by facsimile transmission, (b) on the first business day after it is sent
by air express overnight courier service, or (c) on the third business day
following deposit in the United States mail, registered or certified mail,
return receipt requested, postage prepaid and addressed, to the following
address, as applicable:

                  (1) If to Company, addressed to:

                           Lexicon Genetics Incorporated
                           4000 Research Forest Drive
                           The Woodlands, Texas 77381
                           Attention:  Corporate Secretary

                  (2) If to Executive, addressed to the address set forth below
                      his name on the execution page hereof;

or to such other address as either party may have furnished to the other party
in writing in accordance with this Section 27.

         28. COUNTERPARTS. This Agreement may be executed in any number of
counterparts, each of which when so executed and delivered shall be an original,
but all such counterparts shall together constitute one and the same instrument.
Each counterpart may consist of a copy hereof containing multiple signature
pages, each signed by one party, but together signed by both parties hereto.

         29. EXECUTIVE ACKNOWLEDGMENT; NO STRICT CONSTRUCTION. The Executive
represents to Company that he is knowledgeable and sophisticated as to business
matters, including the subject matter of this Agreement, that he has read the
Agreement and that he understands its terms and

                                                                Initials:_______

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                                       21
<PAGE>   22


     conditions. The parties hereto agree that the language used in this
     Agreement shall be deemed to be the language chosen by them to express
     their mutual intent, and no rule of strict construction shall be applied
     against either party hereto. Executive also represents that he is free to
     enter into this Agreement including, without limitation, that he is not
     subject to any other contract of employment or covenant not to compete that
     would conflict in any way with his duties under this Agreement. Executive
     acknowledges that he has had the opportunity to consult with counsel of his
     choice, independent of Employer's counsel, regarding the terms and
     conditions of this Agreement and has done so to the extent that he, in his
     unfettered discretion, deemed to be appropriate.

          30. SUPERSEDING AGREEMENT. This Employment Agreement shall supersede
     any prior employment agreement entered into between the Company and
     Executive.

              [Intentionally left blank -- signature page follows]







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                                       22
<PAGE>   23

     IN WITNESS WHEREOF, the Executive has hereunto set his hand, and Company
has caused this Agreement to be executed in its name and on its behalf, to be
effective as of the Effective Date first above written.



WITNESS:                                           EXECUTIVE:




Signature:                          Signature:         /s/Randall Riggs
          -----------------------             ---------------------------------
Printed Name:                                             Randall Riggs
             --------------------
Date:                               Date:             December 22, 1998
     ----------------------------        --------------------------------------
                                    Address for Notices:

                                                   222 South Maple Glade Circle
                                                   The Woodlands, Texas  77382
                                                   ----------------------------
ATTEST:                                 LEXICON GENETICS INCORPORATED


By:    /s/ Jean Magdaleno           By:      /s/ Arthur T. Sands
   ----------------------------        -----------------------------------------
Name:  /s/ Jean Magdaleno           Name:    Arthur T. Sands
     --------------------------          ---------------------------------------
Title: Administrative Assistant     Title: President and Chief Executive Officer
      -------------------------           --------------------------------------
Date:  December 21, 1998            Date:  December 21, 1998
     --------------------------          ---------------------------------------