EXECUTIVE EMPLOYMENT AGREEMENT

Exhibit 10.13

EXECUTIVE EMPLOYMENT AGREEMENT

     THIS EMPLOYMENT AGREEMENT is made as of September 8, 2003, (this “Agreement”), by and between IDEXX Laboratories, Inc., a Delaware corporation (the “Company”) and William C. Wallen (the “Executive”).

     The Board of Directors of the Company (the “Board”) has determined that it is in the best interests of the Company and its shareholders to assure that the Company will have the continued dedication of the Executive, notwithstanding the possibility, threat or occurrence of a Change of Control (as defined below) of the Company. The Board believes it is imperative to diminish the inevitable distraction of the Executive by virtue of the personal uncertainties and risks created by a pending or threatened Change of Control and to encourage the Executive’s full attention and dedication to the Company currently and in the event of any threatened or pending Change of Control, and to provide the Executive with compensation and benefits arrangements upon a Change of Control which ensure that the compensation and benefits expectations of the Executive will be satisfied and which are competitive with those of other corporations. Therefore, in order to accomplish these objectives, the Board has caused the Company to enter into this Agreement.

     NOW, THEREFORE, IT IS HEREBY AGREED AS FOLLOWS:

     1.     Certain Definitions.

          (a) The “Effective Date” shall mean the first date during the Change of Control Period (as defined in Section 1(b)) on which a Change of Control (as defined in Section 2) occurs. Anything in this Agreement to the contrary notwithstanding, if a Change of Control occurs and if the Executive’s employment with the Company is terminated prior to the date on which the Change of Control occurs, and if it is reasonably demonstrated by the Executive that such termination of employment (i) was at the request of a third party who has taken steps reasonably calculated to effect a Change of Control or (ii) otherwise arose in connection with or anticipation of a Change of Control, then for all purposes of this Agreement the “Effective Date” shall mean the date immediately prior to the date of such termination of employment.

          (b) The “Change of Control Period” shall mean the period commencing on the date hereof and ending on the second anniversary of the date hereof; provided, however, that commencing on the date one year after the date hereof, and on each annual anniversary of such date (such date and each annual anniversary thereof shall be hereinafter referred to as the “Renewal Date”), unless previously terminated, the Change of Control Period shall be automatically extended so as to terminate three years from such Renewal Date, unless at least 120 days prior to the Renewal Date the Company shall give notice to the Executive that the Change of Control Period shall not be so extended.

     2.     Change of Control. For the purpose of this Agreement, a “Change of Control” shall mean:

          (a) The acquisition by an individual, entity or group (within the meaning of Section 13(d)(3) or 14(d)(2) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”)) (a “Person”) of beneficial ownership (within the meaning of Rule 13d-3 promulgated under the Exchange Act) of 20% or more of either (i) the then-outstanding shares of common stock of the Company (the “Outstanding Company Common Stock”) or (ii) the combined voting power of the then-outstanding voting securities of the Company entitled to vote generally in the election of directors (the “Outstanding Company Voting Securities”); provided, however, that for purposes of this subsection (a), the following acquisitions shall not constitute a Change of Control: (i) any acquisition directly from the Company, (ii) any acquisition by the Company, (iii) any acquisition by any employee benefit plan (or related trust) sponsored or maintained by the Company or any corporation controlled by the Company, or (iv) any acquisition by any corporation pursuant to a transaction which satisfies the criteria set forth in clauses (i), (ii) and (iii) of subsection (c) of this Section 2; or

          (b) Individuals who, as of the date hereof, constitute the Board (the “Incumbent Board”) cease for any reason to constitute at least a majority of the Board; provided, however, that any individual becoming a director subsequently to the date hereof whose election, or nomination for election by the Company’s shareholders, was approved by a vote of at least a majority of the directors then comprising the Incumbent Board shall be considered as though such individual were a member of the Incumbent Board, but excluding, for this purpose, any such individual whose initial assumption of office occurs as a result of an actual or threatened election contest with respect to the election or removal of directors or other actual or threatened solicitation of proxies or consents by or on behalf of a Person other than the Board; or

          (c) Consummation of a reorganization, merger or consolidation or sale or other disposition of all or substantially all of the assets of the Company (a “Business Combination”), in each case, unless, immediately following such Business Combination, (i) all or substantially all of the individuals and entities who were the beneficial owners, respectively, of the Outstanding Company Common Stock and Outstanding Company Voting Securities immediately prior to such Business Combination beneficially own, directly or indirectly, more than 60% of, respectively, the then-outstanding shares of common stock and the combined voting power of the then-outstanding voting securities entitled to vote generally in the election of directors, of the corporation resulting from such Business Combination (which as used in this Section 2(c) shall include, without limitation, a corporation which as a result of such transaction owns the Company or all or substantially all of the Company’s assets either directly or through one or more subsidiaries) in substantially the same proportions as their ownership, immediately prior to such Business Combination of the Outstanding Company Common Stock and Outstanding Company Voting Securities, as the case may be, (ii) no Person (excluding any corporation resulting from such Business Combination or any employee benefit plan (or related trust) of the Company or such corporation resulting from such Business Combination) beneficially owns, directly or indirectly, 20% or more of, respectively, the then outstanding shares of common stock of the corporation resulting from such Business Combination, or the combined voting power of the then-outstanding voting securities of such corporation and (iii) at least half of the members of the board of directors of the corporation resulting from such Business Combination were members of the Incumbent Board at the time of the execution of the initial agreement, or of the action of the Board, providing for such Business Combination; or

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          (d) Approval by the shareholders of the Company of a complete liquidation or dissolution of the Company.

     3.     Employment Period. The Company hereby agrees to continue the Executive in its employ, and the Executive hereby agrees to remain in the employ of the Company subject to the terms and conditions of this Agreement, for the period commencing on the Effective Date and ending on the earlier of (i) the second anniversary of such date or (ii) the termination of the Executive’s employment pursuant to Section 5 hereof (the “Employment Period”). Except as provided in Section 1(a), nothing in this Agreement shall, prior to the Effective Date, impose upon the Company any obligation to retain the Executive as an employee. In addition, nothing in this Agreement shall restrict the Executive from terminating his employment with the Company, and no such termination by the Executive shall be deemed a breach of this Agreement.

     4.     Terms of Employment.

          (a) Position and Duties.

               (i) During the Employment Period, (A) the Executive’s position (including status, offices, titles and reporting requirements), authority, duties and responsibilities shall be at least commensurate in all material respects with the most significant of those held, exercised and assigned at any time during the 120-day period immediately preceding the Effective Date and (B) the Executive’s services shall be performed at the location where the Executive was employed immediately preceding the Effective Date or any office or location less than 35 miles from such location.

               (ii) During the Employment Period, and excluding any periods of vacation and sick leave to which the Executive is entitled, the Executive agrees to devote reasonable attention and time during normal business hours to the business and affairs of the Company and, to the extent necessary to discharge the responsibilities assigned to the Executive hereunder, to use the Executive’s reasonable best efforts to perform faithfully and efficiently such responsibilities. During the Employment Period it shall not be a violation of this Agreement for the Executive to (A) serve on corporate, civic or charitable boards or committees, (B) deliver lectures, fulfill speaking engagements or teach at educational institutions, and (C) manage personal investments, so long as such activities do not significantly interfere with the performance of the Executive’s responsibilities as an employee of the Company or the terms of this Agreement. It is expressly understood and agreed that to the extent that any such activities have been conducted by the Executive prior to the Effective Date, the continued conduct of such activities (or the conduct of activities similar in nature and scope thereto) subsequent to the Effective Date shall not thereafter be deemed to interfere with the performance of the Executive’s responsibilities to the Company.

          (b) Compensation.

               (i) Base Salary. During the Employment Period, the Executive shall receive an annual base salary (“Annual Base Salary”), which shall be paid at a monthly rate, at least equal to twelve times the highest monthly base salary paid or payable, including any base salary which has been earned but deferred, to the Executive by the Company and its affiliated

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companies in respect of the twelve-month period immediately preceding the month in which the Effective Date occurs. During the Employment Period, the Annual Base Salary shall be reviewed no more than 12 months after the last salary increase awarded to the Executive prior to the Effective Date and thereafter at least annually. Any increase in Annual Base Salary shall not serve to limit or reduce any other obligation to the Executive under this Agreement. Annual Base Salary shall not be reduced after any such increase and the term Annual Base Salary as utilized in this Agreement shall refer to Annual Base Salary as so increased. As used in this Agreement, the term “affiliated companies” shall include any company controlled by, controlling or under common control with the Company.

               (ii) Annual Bonus. In addition to Annual Base Salary, the Executive shall be entitled to receive such annual bonus as may be determined by the Board of Directors, but in no event less than the annual bonus paid or payable in respect of the full fiscal year immediately preceding the Effective Date.

               (iii) Incentive Plans. During the Employment Period, the Executive shall be entitled to participate in all incentive plans, practices, policies and programs applicable generally to other peer executives of the Company and its affiliated companies, but in no event shall such plans, practices, policies and programs provide the Executive with benefits which are less favorable, in the aggregate, than the most favorable of such plans, practices, policies and programs in effect for the Executive at any time during the 120-day period immediately preceding the Effective Date or, if more favorable to the Executive, those provided generally at any time after the Effective Date to other peer executives of the Company and its affiliated companies.

               (iv) Welfare Benefit, Savings and Retirement Plans. During the Employment Period, the Executive and/or the Executive’s family, as the case may be, shall be eligible for participation in and shall receive all benefits under welfare benefit, savings and retirement plans, practices, policies and programs provided by the Company and its affiliated companies (including, without limitation, medical, prescription, dental, disability, employee life, group life, split-dollar life, accidental death and travel accident insurance plans and programs) to the extent applicable generally to other peer executives of the Company, but in no event shall such plans, practices, policies and programs provide the Executive with benefits which are less favorable, in the aggregate, than the most favorable of such plans, practices, policies and programs in effect for the Executive at any time during the 120-day period immediately preceding the Effective Date or, if more favorable to the Executive, those provided generally at any time after the Effective Date to other peer executives of the Company and its affiliated companies.

               (v) Expenses. During the Employment Period, the Executive shall be entitled to receive reimbursement for all reasonable expenses incurred by the Executive in accordance with the policies, practices and procedures of the Company in effect immediately prior to the Effective Date.

               (vi) Vacation. During the Employment Period, the Executive shall be entitled to paid vacation in accordance with the plans, policies, programs and practices of the Company and its affiliated companies, but in no event shall such plans, practices, policies and

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programs provide the Executive with benefits which are less favorable, in the aggregate, than the most favorable of such plans, practices, policies and programs in effect for the Executive at any time during the 120-day period immediately preceding the Effective Date or, if more favorable to the Executive, those provided generally at any time after the Effective Date to other peer executives of the Company and its affiliated companies.

          (c) Options. Upon the occurrence of a Change of Control, all outstanding options to purchase shares of Common Stock held by the Executive shall become immediately exercisable in full.

     5.     Termination of Employment.

          (a) Death or Disability. The Executive’s employment shall terminate automatically upon the Executive’s death during the Employment Period. If the Company determines in good faith that the Disability of the Executive has occurred during the Employment Period (pursuant to the definition of Disability set forth below), it may give to the Executive written notice in accordance with Section 12(b) of this Agreement of its intention to terminate the Executive’s employment. In such event, the Executive’s employment with the Company shall terminate effective on the 30th day after receipt of such notice by the Executive (the “Disability Effective Date”), provided that, within the 30 days after such receipt, the Executive shall not have returned to full-time performance of the Executive’s duties. For purposes of this Agreement, “Disability” shall mean the absence of the Executive from the Executive’s duties with the Company on a full-time basis for 180 consecutive business days as a result of incapacity due to mental or physical illness which is determined to be total and permanent by a physician selected by the Company or its insurers and acceptable to the Executive or the Executive’s legal representative.

          (b) Cause. Subject to Section 5(d), the Company may terminate the Executive’s employment during the Employment Period for Cause. For purposes of this Agreement, “Cause” shall mean:

For purposes of this provision, no act or failure to act, on the part of the Executive, shall be considered “willful” unless it is done, or omitted to be done, by the Executive in bad faith or without reasonable belief that the Executive’s action or omission was in the best interests of the Company.

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          (c) Good Reason. The Executive’s employment may be terminated by the Executive with or without Good Reason. For purposes of this Agreement, “Good Reason” shall mean:

     For purposes of this Section 5(c), any good faith determination of “Good Reason” made by the Executive shall be conclusive.

     Anything in this Agreement to the contrary notwithstanding, a termination by the Executive for any reason during the 30-day period immediately following the first twelve (12) months after the Effective Date shall be deemed to be a termination for Good Reason for all purposes of this Agreement.

          (d) Notice of Termination.

               (i) Any termination by the Company for Cause, or by the Executive for Good Reason, shall be effected by Notice of Termination to the other party hereto given in accordance with Section 12(b) of this Agreement. For purposes of this Agreement, a “Notice of Termination” means a written notice which (i) indicates the specific termination provision in this Agreement relied upon, (ii) to the extent applicable, 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 and (iii) if the Date of Termination (as defined below) is other than the date of receipt of such notice, specifies the termination date (which date shall be not more than thirty days after the giving of such notice). The failure by the Executive or the Company to set

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