Document:

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                                                                    Exhibit 10.3

                            IDEXX LABORATORIES, INC.

                           1991 DIRECTOR OPTION PLAN

                             (AS OF JULY 21, 1999)

        1.     PURPOSE

               The purpose of this 1991 Director Option Plan (the "Plan") of
IDEXX Laboratories, Inc. (the "Company") is to encourage ownership in the
Company by outside directors of the Company whose continued services are
considered essential to the Company's future progress and to provide them with a
further incentive to remain as directors of the Company.

        2.     ADMINISTRATION

               The Board of Directors shall supervise and administer the Plan.
Grants of stock options under the Plan and the amount and nature of the awards
to be granted shall be automatic in accordance with Section 5. However, all
questions of interpretation of the Plan or of any options issued under it shall
be determined by the Board of Directors and such determination shall be final
and binding upon all persons having an interest in the Plan.

        3.     PARTICIPATION IN THE PLAN

               Directors of the Company who are not employees of the Company or
any subsidiary of the Company shall be eligible to participate in the Plan.

        4.     STOCK SUBJECT TO THE PLAN

               (a) The maximum number of shares which may be issued under the
Plan shall be 500,000 shares of the Company's Common Stock, par value $.10 per
share ("Common Stock"), subject to adjustment as provided in Section 9 of the
Plan.

               (b) If any outstanding option under the Plan for any reason
expires or is terminated without having been exercised in full, the shares
allocable to the unexercised portion of such option shall again become available
for grant pursuant to the Plan.

               (c) All options granted under the Plan shall be non-statutory
options not entitled to special tax treatment under Section 422 of the Internal
Revenue Code of 1986, as amended to date and as it may be amended from time to
time (the "Code").

        5.     TERMS, CONDITIONS AND FORM OF OPTIONS

               Each option granted under the Plan shall be evidenced by a
written agreement in such form as the Board of Directors shall from time to time
approve, which agreements shall comply with and be subject to the following
terms and conditions:

               (a) OPTION GRANT DATES. Options shall be granted (i) to all
eligible directors who are directors as of April 24, 1991 on each date that he
or she is re-elected as a director, and (ii) to all other eligible directors
upon his or her initial election as a director and on each subsequent date that
he or she is re-elected as a director.

               (b) SHARES SUBJECT TO OPTION. Except as provided below, each
option granted under the Plan shall be exercisable for 20,000 shares of Common
Stock. Notwithstanding anything to the contrary contained herein, the

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number of shares for which an option is granted under the Plan shall be reduced
below 20,000 shares of Common Stock (and the exercise period adjusted) in the
event of the following:

                      (1) If, after April 24, 1991, a director is initially
               elected other than at an annual meeting of stockholders and such
               director is re-elected at the next annual meeting of
               stockholders, then:

                              (i) the option granted to such director under the
                      Plan in connection with his re-election (the "Second
                      Option") shall be exercisable for such number of shares as
                      is determined by multiplying 18.268493 (which is 6,668
                      divided by 365) by the number of days between (a) the date
                      which is the third anniversary of the date of grant of the
                      option received by such director under the Plan on the
                      date of his initial election as a director and (b) the
                      date which is the third anniversary of the date of grant
                      of the Second Option; and

                              (ii) all of such shares shall become exercisable
                      on the third anniversary of the date of grant of the
                      Second Option.

                      (2) If a director elected at an annual meeting of
               stockholders is re-elected at a subsequent annual meeting of
               stockholders which is earlier than the third annual meeting of
               stockholders following his prior election, then:

                              (i) the option granted to such director under the
                      Plan in connection with his re-election (the "Subsequent
                      Option") shall be exercisable for either (a) 6,668 shares,
                      if the annual meeting at which such director is re-elected
                      is the first annual meeting following his prior election
                      or (b) 13,334 shares, if the annual meeting at which such
                      director is re-elected is the second annual meeting
                      following his prior election;

                              (ii) if the number of shares under the Subsequent
                      Option is 13,334, then 6,666 shares shall become
                      exercisable on the second anniversary of the date of grant
                      of the Subsequent Option and 6,668 shares shall become
                      exercisable on the third anniversary of the date of grant
                      of the Subsequent Option; and

                              (iii) if the number of shares under the Subsequent
                      Option is 6,668, then all of such shares shall become
                      exercisable on the third anniversary of the date of grant
                      of the Subsequent Option.

               (c) OPTION EXERCISE PRICE. The option exercise price per share
for each option granted under the Plan shall equal (i) the last reported sales
price per share of the Company's Common Stock on the NASDAQ National Market
System (or, if the Company is traded on a nationally recognized securities
exchange on the date of grant, the reported closing sales price per share of the
Company's Common Stock by such exchange) on the date of grant (or if no such
price is reported on such date such price as reported on the nearest preceding
day) or (ii) if the Common Stock is not traded on NASDAQ or any exchange, the
fair market value per share on the date of grant as determined by the Board of
Directors.

               (d) LIMITED TRANSFERABILITY. Each option granted under the Plan
shall not be transferable by the optionee otherwise than (i) by will, or by the
laws of descent and distribution, or (ii) with the approval of the Board of
Directors, by gift to (A) one or more members of the optionee's family or
entities controlled by, or for the benefit of the optionee or such family
members, or (B) to one or more charitable organizations (including charitable
trusts). Except as the Board of Directors may otherwise determine, no option or
interest therein may be transferred, assigned, pledged or hypothecated by the
optionee during his lifetime, whether by operation of the law or otherwise, or
be made subject to execution, attachment or similar process.

               (e) EXERCISE PERIOD. Each option may be exercised on a cumulative
basis as to one-third of the shares subject to the option on each of the first,
second and third anniversaries of the date of grant of such option, provided
that, subject to the provisions of Section 5(f), no option may be exercised more

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than 90 days after the optionee ceases to serve as a director of the Company. No
option shall be exercisable after the expiration of ten years from the date of
grant.

               (f) EXERCISE PERIOD UPON DISABILITY OR DEATH. Notwithstanding the
provisions of Section 5(e), any option granted under the Plan may be exercised,
to the extent then exercisable, by an optionee who becomes disabled (within the
meaning of Section 22(e)(3) of the Code or any successor provision thereto)
while acting as a director of the Company, or may be exercised, to the extent
then exercisable, upon the death of such optionee while a director of the
Company by the person to whom it is transferred by will, by the laws of descent
and distribution, or by written notice filed pursuant to Section 5(h), in each
case within the period of one year after the date the optionee ceases to be such
a director by reason of such disability or death; provided that, no option shall
be exercisable after the expiration of ten years from the date of grant.

               (g) EXERCISE PROCEDURE. Options may be exercised only by written
notice to the Company at its principal office accompanied by payment in cash of
the full consideration for the shares as to which they are exercised.

               (h) EXERCISE BY REPRESENTATIVE FOLLOWING DEATH OF DIRECTOR. A
director, by written notice to the Company, may designate one or more persons
(and from time to time change such designation) including his legal
representative, who, by reason of the director's death, shall acquire the right
to exercise all or a portion of the option. If the person or persons so
designated wish to exercise any portion of the option, they must do so within
the term of the option as provided herein. Any exercise by a representative
shall be subject to the provisions of the Plan.

        6.     ASSIGNMENTS

               The rights and benefits under the Plan may not be assigned except
for the designation of a beneficiary as provided in Section 5.

        7.     TIME FOR GRANTING OPTIONS

               All options for shares subject to the Plan shall be granted, if
at all, not later than five years after the approval of the Plan by the
Company's stockholders.

        8.     LIMITATION OF RIGHTS

               (a) NO RIGHT TO CONTINUE AS A DIRECTOR. Neither the Plan, nor the
granting of an option nor any other action taken pursuant to the Plan, shall
constitute or be evidence of any agreement or understanding, express or implied,
that the Company will retain a director for any period of time.

               (b) NO STOCKHOLDERS' RIGHTS FOR OPTIONS. An optionee shall have
no rights as a stockholder with respect to the shares covered by his options
until the date of the issuance to him of a stock certificate therefor, and no
adjustment will be made for dividends or other rights (except as provided in
Section 9) for which the record date is prior to the date such certificate is
issued.

        9.     CHANGES IN COMMON STOCK

               (a) If the outstanding shares of Common Stock are increased,
decreased or exchanged for a different number or kind of shares or other
securities, or if additional shares or new or different shares or other
securities are distributed with respect to such shares of Common Stock or other
securities, through merger, consolidation, sale of all or substantially all of
the assets of the Company, reorganization, recapitalization, reclassification,
stock dividend, stock split, reverse stock split or other distribution with
respect to such shares of Common Stock, or other securities, an appropriate and
proportionate adjustment will be made in (i) the maximum number and kind of
shares reserved for issuance under the Plan, (ii) the number and kind of shares
or other securities subject to then outstanding options under the Plan and (iii)
the price for each share subject to any then outstanding options under the Plan,
without changing the aggregate purchase price as to which such options remain
exercisable. No fractional shares will be issued under the Plan on account of
any such adjustments.

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               (b) In the event that the Company is merged or consolidated into
or with another corporation (in which consolidation or merger the stockholders
of the Company receive distribution of cash or securities of another issuer as a
result thereof), or in the event that all or substantially all of the assets of
the Company are acquired by any other person or entity, or in the event of a
reorganization or liquidation of the Company, the Board of Directors of the
Company or the board of directors of any corporation assuming the obligations of
the Company, shall, as to outstanding options, either (i) provide that such
options shall be assumed, or equivalent options shall be substituted, by the
acquiring or successor corporation (or an affiliate thereof), or (ii) upon
written notice to the optionees, provide that all unexercised options will
terminate immediately prior to the consummation of such merger, consolidation,
acquisition, reorganization or liquidations unless exercised by the optionee
within a specified number of days following the date of such notice.

        10.    AMENDMENT OF THE PLAN

               The Board of Directors may suspend or discontinue the Plan or
review or amend it in any respect whatsoever; provided, however, that without
approval of the stockholders of the Company no revision or amendment shall
change the number of shares subject to the Plan (except as provided in Section
9), change the designation of the class of directors eligible to receive
options, or materially increase the benefits accruing to participants under the
Plan. The Plan may not be amended more than once in any six-month period.

        11.    NOTICE

               Any written notice to the Company required by any of the
provisions of the Plan shall be addressed to the Treasurer of the Company and
shall become effective when it is received.

        12.    GOVERNING LAW

               The Plan and all determinations made and actions taken pursuant
hereto shall be governed by the laws of the State of Delaware.

         Approved by the Board of Directors on April 24, 1991

         Approved by the Stockholders on June 10, 1991

         Amended by the Board of Directors on December 15, 1992

         Amended by the Board of Directors on February 26, 1993, with amendment
         to become effective on June 16, 1993 after approval by Stockholders

         Amendment approved by Stockholders on May 18, 1993, with amendment
         effective on June 16, 1993

         Number of shares covered by the Plan reflects 2 for 1 stock split in
         the form of a stock dividend paid on October 1, 1993

         Amended by the Board of Directors on February 9, 1995

         Amendment approved by Stockholders on May 26, 1995

         Number of shares covered by the Plan reflects 2 for 1 stock split in
         the form of a stock dividend paid on June 5, 1995

         Amended by the Board of Directors on March 5, 1996; amendment approved
         by the Stockholders on May 24, 1996.

         Amended by the Board of Directors on July 21, 1999.

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                                        CONFIDENTIAL MATERIAL OMITTED AND
                                        FILED SEPARATELY WITH THE SECURITIES AND
                                        EXCHANGE COMMISSION (*Denotes Omission)
                                              EXHIBIT 10.6d (REDACTED)

                 Fifth Amendment to the IDEXX Laboratories, Inc.
                      and Ortho-Clinical Diagnostics, Inc.
               (as successor in interest to Eastman Kodak Company)
                     Supply Agreement dated January 15, 1992

This Amendment (the "AMENDMENT") is effective as of January 1, 1999, by and
between Ortho-Clinical Diagnostics, Inc. (formerly known as Johnson & Johnson
Clinical Diagnostics, Inc.), a New York corporation with offices at 100 Indigo
Creek Drive, Rochester, N.Y. ("OCD"), and IDEXX Laboratories, Inc., a Delaware
corporation, with offices at One IDEXX Drive, Westbrook, Maine, 04092 ("IDEXX").

WHEREAS OCD and IDEXX desire to amend the Supply Agreement dated January 15,
1992, as amended on November 16, 1993, November 19, 1993, March 15, 1994 and
January 1, 1996 (such Supply Agreement as so amended being hereinafter referred
to as the "SUPPLY AGREEMENT") as provided herein:

NOW, THEREFORE, in consideration of the premises and the mutual agreements
contained herein, the parties hereto agree as follows:

1. All references to Johnson & Johnson Clinical Diagnostics Systems, Inc. or
JJCD shall be deemed to be replaced by reference to Ortho-Clinical Diagnostics,
Inc. or OCD.

2. In Clause 1, the following definitions are hereby deleted in their entirety
and replaced with the following:

   "the Term"               The period from January 1, 1999 until December 31,
                            2010.

   "the VETTEST analyzer"   The VETTEST VT 8008 analyzer developed by or on
                            behalf of VETTEST S.A., predecessor of IDEXX, for
                            veterinary purposes and using VITROS slides;
                            including (i) any updates or modifications to such
                            analyzer, or (ii) other chemistry testing
                            instrument which, in the case of clause(i) and
                            (ii), is designed by IDEXX to be the bridging
                            instrument to a next-generation veterinary
                            chemistry analyzer ***********
                            ***********************************

   "the VETTEST slides"     VITROS or other OCD chemistry slides specially bar
                            coded, labeled, and/or packaged for the VETTEST
                            analyzer in

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                             accordance with the terms of this Agreement and
                             supplied by OCD in accordance with the terms and
                             conditions of this Agreement.

3.      In Clause 1, insert the following terms:

   "the Effective Rebate Rate"  For any year, the weighted average percentage
                                reduction in the purchase price of any slides
                                purchased in such year that IDEXX is entitled to
                                receive pursuant to Section 7.03 hereunder.  The
                                calculation of the Effective Rebate Rate is
                                illustrated in Schedule 10.

   "the Prime Rate"             For any day in any calendar month, the prime
                                rate of interest as published in the WALL STREET
                                JOURNAL on the last business day of the
                                immediately preceding month.

   *********************        *****************************
                                *********************************
                                ********

4.      Sub-Clause 5.01 is hereby deleted in its entirety and is replaced by the
        following:

        5.01    Attached hereto as SCHEDULE 7 are Purchase Commitments by IDEXX
                for VETTEST slides for calendar years 1999 through and including
                2006. The Purchase Commitments constitute IDEXX's anticipated
                minimum aggregate purchase quantities for single chemistry
                VETTEST slides and PANELS/PROFILES slides in the indicated
                calendar years. For calendar years 2007 through and including
                2010, IDEXX shall advise OCD of the Purchase Commitment for each
                such year not later than October 1 of the preceding year, and
                upon receipt by OCD, such Purchase Commitments shall be deemed
                to be incorporated into SCHEDULE 7. IDEXX's aggregate Purchase
                Commitment for the period 2007 through and including 2010 shall
                be not less than ********** slides.

                During each of calendar years 2000 through and including 2002,
                IDEXX shall purchase not less than ***************** single
                slides; during each of calendar years 2003 through and including
                2006, IDEXX shall purchase not less than *************** single
                slides; and during each of the calendar years 2007 through and
                including 2010, IDEXX shall purchase a minimum number of single
                slides egual to *** of the total Purchase Commitment for such
                year.

                Failure by IDEXX to purchase at least the indicated Purchase
                Commitment quantities of each type of slides in any year may
                subject IDEXX to the

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                requirement to make a payment to OCD as set forth in sub-Clause
                5.02 below, but such failure shall in no event otherwise be
                deemed to be a breach of this Agreement.

5.      Sub-Clause 5.04 is hereby deleted in its entirety and is replaced by the
        following:

        5.04    Not later than October 1 of each calendar year commencing
                October 1, 1999, IDEXX shall notify OCD of forecasted
                requirements for the subsequent year for each of the VETTEST
                slides (single slides and PANELS/PROFILES slides) (each such
                notification, a "PURCHASE FORECAST"), and the order quantities
                in the subsequent year for each of the VETTEST slides shall be
                within+/-25% of the such Purchase Forecast unless the parties
                otherwise agree. As long as slide orders are within the
                indicated range of+/-25% of the applicable Purchase Forecast,
                OCD shall deliver the slides in accordance with the orders. The
                Purchase Forecasts constitute non-binding forecasts which shall
                be the basis for determining IDEXX's quarterly cash rebate
                pursuant to sub-Clause 7.03 below.

6.      Sub-Clause 7.03 is hereby deleted in its entirety and is replaced by the
        following:

        7.03    Beginning with slide purchases made during calendar year 2000
                (which, for the avoidance of doubt, shall not include any slides
                shipped by OCD in calendar year 2000 to fulfill IDEXX's total
                1999 purchase order for ********* slides), IDEXX shall be
                entitled to receive a cash rebate in the amounts set forth below
                for total slide purchases that, in any year, exceed the
                quantities set forth below as follows:

                 Annual Slide Purchases              Incremental Cash Rebate -
                                                        % Off Purchase Price
                     **************                              **
                 **********************                         ***
                 **********************                         ***
                 **********************                         ***
                 **********************                         ***
                 **********************                         ***
                 **********************                         ***

                The rebate amounts set forth above constitute a percentage
                reduction in the purchase price of any slides (including both
                single slides and PANELS/PROFILES slides) purchased above the
                corresponding quantity. The percentage amounts are incremental
                (as opposed to cumulative) and relate only to the quantities set
                forth opposite it. For example, if IDEXX were to purchase **
                **** in any one calendar year, it would not be entitled to
                a *** price reduction on all slides that it purchased in such
                year, rather, it would be entitled to receive (i) ** purchase
                price reduction on the first ********* slides purchased,

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                (ii) a *** purchase price reduction on all slides purchased over
                ********** up to and including ********* (iii) an *** purchase
                price reduction on all slides purchased over ************* up to
                and including ********** and (iv) a return *** purchase price
                reduction on all slides purchased over **************** up to
                and including the ********** slides that it purchased. The
                foregoing notwithstanding, it is understood and agreed that if
                IDEXX does not achieve the Purchase Commitments set forth above
                in any calendar year, then IDEXX shall not be entitled to
                receive a rebate for such year.

                In the beginning of each calendar year, beginning with calendar
                year 2000, OCD shall calculate an estimated Effective Rebate
                Rate (the "ESTIMATED REBATE RATE") based on the lesser of (i)
                IDEXX's Purchase Forecast for such year and (ii) **** of the
                total number of slides that IDEXX purchased in the immediately
                preceding calendar year. Not later than thirty (30) days after
                the end of each of the first three calendar quarters in any
                calendar year (or thirty days after IDEXX completes payment in
                full for slides purchased during such quarter, if later), OCD
                shall pay to IDEXX an amount equal to the estimated rebate
                payment that IDEXX would be entitled to receive in such quarter
                (the "ESTIMATED REBATE PAYMENT"). The Estimated Rebate Payment
                for any quarter shall be calculated by (i) multiplying the
                Estimated Rebate Rate in effect during such quarter by the total
                purchase price for the VETTEST slides purchased by IDEXX during
                such quarter and (ii) subtracting from such amount an amount
                equal to *** of the total calculated in clause (i) above. The
                foregoing notwithstanding, if, in any calendar year, (i) IDEXX's
                total slide orders for the immediately preceding calendar year
                were less than *** of its Purchase Forecast for such preceding
                calendar year or (ii) OCD determines, in its reasonable
                discretion, at anytime after the end of the second calendar
                quarter of such calendar year, that IDEXX is reasonably unlikely
                to meet its Purchase Forecast for such year, then OCD shall have
                the right to recalculate the Estimated Rebate Rate based on
                IDEXX's Purchase Commitment for such year (such recalculated
                rate being hereinafter referred to as the "New Estimated Rebate
                Rate"). If OCD elects to recalculate the Estimated Rebate Rate
                pursuant to the immediately preceding sentence, (i) OCD shall
                notify IDEXX in writing which notice shall set forth the New
                Estimated Rebate Rate, (ii) OCD shall calculate all remaining
                quarterly Estimated Rebate Payments (which may include the
                Estimated Rebate Payment for the second calendar quarter) using
                the New Estimated Rebate Rate and (iii) all such Estimated
                Rebate Payments shall be made in accordance with this sub-clause
                7.03, except that such Estimated Rebate Payments shall be less
                the amount by which the Estimated Rebate Payments received by
                IDEXX during the then current calendar year exceed the Estimated
                Rebate Payments IDEXX would have received during such calendar
                year if the New Estimated Rebate Rate were in effect from the
                first day of such calendar year. Notwithstanding any provision
                in this Agreement to the contrary, OCD shall not be required to
                make any Estimated Rebate Payments to IDEXX in any calendar

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                year if (A) any amounts payable to OCD from IDEXX pursuant to
                this Agreement are overdue, unless such amounts are being
                disputed in good faith by IDEXX, or (B) OCD determines in its
                reasonable judgment that IDEXX is reasonably unlikely to meet
                its Purchase Commitments for such year. In the case of clause
                (B) above, OCD shall have the right to make such determination
                at any time after the end of the second calendar quarter of any
                calendar year (or at the beginning of such calendar year if
                IDEXX's Purchase Forecast for such year is less than its
                Purchase Commitment for such year) provided that OCD has
                consulted with IDEXX and given IDEXX an opportunity (which
                opportunity shall be available for a period of not less than 5
                business days nor more than 10 business days) to demonstrate its
                intent and ability to meet its Purchase Commitments for such
                year. For the avoidance of doubt, OCD's obligation to make any
                Estimated Rebate Payments shall be suspended during the period
                referred to in the immediately preceding sentence and the days
                in such period shall not be counted when determining the date by
                which the next scheduled Estimated Rebate Payment is due and
                payable. If, after fulfilling the requirements set forth in this
                paragraph, OCD makes the determination described in clause (B)
                above, OCD (i) shall promptly notify IDEXX in writing of its
                determination and (ii) shall thereafter have the right to cease
                making Estimated Rebate Payments for the remainder of such
                calendar year.

                Not later than thirty (30) business days after the end of the
                last calendar quarter of any calendar year (or thirty days after
                IDEXX completes payment in full for slides purchased during such
                quarter, if later), OCD shall pay to IDEXX the amount by which
                (i) the Effective Rebate Rate multiplied by the total purchase
                price for VETTEST slides purchased by IDEXX during such calendar
                year exceeds (ii) the aggregate amount of the Estimated Rebate
                Payments made by OCD to IDEXX during such calendar year. If the
                amount in clause (ii) above exceeds the amount in clause (i)
                above, OCD shall deliver to IDEXX a written notice of such fact
                (a "Reimbursement Notice") and IDEXX shall pay to OCD, within
                thirty (30) days of receipt of such notice an amount in cash
                equal to the amount of such excess.

                Notwithstanding the foregoing, (i) if any amounts payable to OCD
                from IDEXX pursuant to this Agreement are overdue, other than
                amounts that are being disputed in good faith by IDEXX, then OCD
                shall be entitled to withhold such overdue amount (plus any
                accrued interest) from any rebate payments to which IDEXX may be
                entitled and (ii) if IDEXX does not achieve its Purchase
                Commitment in any given calendar year, then IDEXX shall return
                all Estimated Rebate Payments received from OCD for such year no
                later than thirty (30) days after the end of such calendar year.

                Any overdue payments by OCD or IDEXX of any amounts owed to the
                other pursuant to this sub-clause 7.03 shall bear interest at a
                rate per annum equal to*** **********. Such interest shall be
                payable at the same time as the payment to

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                which it relates and shall be calculated daily on the basis of a
                year of 365 days and the actual number of days elapsed.

                OCD shall prepare a remittance advice to accompany each rebate
                payment (or Reimbursement Notice), which shall set forth the
                reporting period for which the payment is made (or demanded) and
                a summary sheet which shall detail OCD's calculation of the
                rebate (or reimbursement). If IDEXX disagrees with the rebate or
                reimbursement calculation, IDEXX shall promptly notify OCD, and
                the parties shall review the calculations together in good faith
                to agree on any appropriate corrections or adjustments.

                An illustrative representation of the foregoing rebate
                calculation methodology is attached hereto as SCHEDULE 10.

7.      SCHEDULE 7 to the Agreement is hereby deleted in its entirety and
        replaced by SCHEDULE 7 attached hereto.

8.      Clause 31 is hereby added to the Agreement as follows:

        31.     1999 REBATE

                If during calendar year 1999 IDEXX sells worldwide any of the
                total slide volumes set forth below (counting both single slides
                and PANELS/PROFILES slides), IDEXX shall be entitled to a cash
                rebate in the amount set forth opposite such sales volume:

                1999 Worldwide Slide Sales           Total Cash Rebate
                        ***********                          **
                  ***********************               ************
                  ***********************               ************
                        ***********                     ************

                The cash rebates above are not incremental or cumulative. For
                the avoidance of doubt, the maximum rebate payment that IDEXX
                could qualify for under this Clause 31 is *********. IDEXX shall
                provide OCD with estimated sales volume information for calendar
                year 1999 not later than December 15, 1999. Not later than
                January 31, 2000, IDEXX shall provide OCD with 1999 actual slide
                sales volume information and, at any time that OCD may
                reasonably request, any other supporting information or
                documentation that OCD may reasonably request. OCD shall
                calculate IDEXX's rebate accordingly, and shall remit to IDEXX
                the total rebate amount not later than (i) February 15, 2000 or,
                if later, (ii) five (5) business days after receipt by OCD, to
                its reasonable satisfaction, of all information which it
                requested pursuant to the immediately preceding sentence. Any
                overdue payments by OCD shall bear interest at a rate per annum
                equal to

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                ***********. Such interest shall be payable at the same time as
                the payment to which it relates and shall be calculated daily on
                the basis of a year of 365 days and the actual number of days
                elapsed.

9.      Clause 32 is hereby added to the Agreement as follows:

        32.     PACKAGING LINE CAPACITY

                The parties agree that OCD shall make a capital investment to
                increase the through-put capacity of the Individual Slide
                Packaging ("ISP") line. OCD estimates the total capital and
                validation costs to increase the capacity of the ISP line to be
                ***********. If at any time OCD has reason to believe that the
                total capital and validation costs will exceed its estimate by
                more than ***, OCD shall promptly notify IDEXX and thereafter,
                OCD and IDEXX shall form a joint team, consisting of two
                representatives from each party. Such team will cooperate in
                determining the most efficient and cost effective way to
                increase the capacity of the ISP line taking into account the
                measures that have been taken, and the costs that have been
                incurred, up to that time. The parties agree to implement the
                recommendations of the joint team.

                The capital and validation costs to increase the capacity of the
                ISP line shall be borne by OCD. If, however, IDEXX does not
                achieve, during the combined calendar years 2000 and 2001, its
                aggregate Purchase Commitments for such years, then IDEXX shall
                reimburse OCD ******************** of such costs within thirty
                (30) days after receipt of reasonably detailed documentation
                supporting such costs. Any overdue payments by IDEXX shall bear
                interest at a rate per annum equal to ************. Such
                interest shall be payable at the same time as the payment to
                which it relates and shall be calculated daily on the basis of a
                year of 365 days and the actual number of days elapsed. IDEXX
                shall have the right to assume responsibility for packaging
                PANELS/PROFILES slides.

                If IDEXX elects to exercise such right, then (i) IDEXX shall
                notify OCD in writing that it proposes to assume such
                responsibility and (ii) thereafter, the parties shall cooperate
                in developing and implementing a plan to effect such a
                transition in a mutually acceptable timeframe, which timeframe
                shall in no event be less than six (6) months from the date OCD
                receives the notice described in clause (i) above.

10.     Clause 33 is hereby added to the Agreement as follows:

        33.     COST SAVING INITIATIVES

                The parties will form a joint team prior to March 31, 2000,
                consisting of two representatives from each party. Such team
                will cooperate to identify potential savings for both parties
                relating to slide manufacturing, post-cartridge packaging,

                                        7
<PAGE>   8

                purchasing, delivery schedules and quality testing processes. If
                this team identifies cost reduction opportunities, and both
                parties reasonably and mutually agree to implement such cost
                reductions, then the parties shall share equally in any cost
                savings.

                The parties shall form an additional joint team prior to March
                31, 2000, consisting of two representatives from each party.
                Such team will cooperate to identify areas of potential savings
                for IDEXX in the distribution process. If this team identifies
                distribution cost reduction opportunities, and both parties
                reasonably and mutually agree to implement such cost reductions,
                then the parties shall share in any cost savings in such
                proportion as they mutually and in good faith agree. The parties
                agree that if OCD distributes slides directly to IDEXX's
                distributors or end-user customers, OCD would invoice IDEXX for
                distribution services in the same manner that billing for slide
                products is currently administered under sub-Clause 8.01 of this
                Agreement.

11.     Clause 34 is hereby added to the Agreement as follows:

        ***     *******************

                ***************************************************************
                ***************************************************************
                ***************************************************************
                ***************************************************************
                ***************************************************************
                ****************************************

                                        8
<PAGE>   9

12.     Clause 35 is hereby added to the Agreement as follows:

        35.     INCREMENTAL SALES OPPORTUNITIES

                If IDEXX provides OCD with specific documentation regarding
                ******************************* that would require IDEXX to
                purchase a number of slides over and above its Purchase
                Commitments for any year and would **************************
                ***************************************************************,
                OCD agrees, upon receipt of any additional information
                that OCD may reasonably request regarding such
                *****************, to negotiate in good faith to reach agreement
                with IDEXX on *************************************************
                ****************** and any other related terms and conditions.
                It is understood and agreed that any slides which IDEXX
                purchases from OCD ********************************************
                *************************, shall be excluded from the
                determination of IDEXX's slide purchases for purposes of
                achieving its Purchase Committments and the determination of any
                rebate entitlement under sub-Clause 7.03 of the Agreement.

13.     Except as modified by this Fifth Amendment, all terms and conditions of
        the Supply Agreement shall continue in full force and effect.

                                       9
<PAGE>   10

IN WITNESS WHEREOF, each of the parties have caused this Agreement to be
executed by its duly authorized officer to be effective as of the date first
above written.

ORTHO-CLINICAL                               IDEXX LABORATORIES, INC.
DIAGNOSTICS, INC.

By: /s/ David A. Rowan                       By: /s/ Louis W. Pollock
   ----------------------------------           -------------------------------
   David A. Rowan,                              Louis W. Pollock,
   Vice President, Corporate Accounts           President,
                                                Professional Office Diagnostics
                                                Division

By: /s/ Cathy Burzik
   ----------------------------------
   Cathy Burzik
   President,
   Ortho-Clinical Diagnostics, Inc.

                                       10
<PAGE>   11

                        SCHEDULE 7 - PURCHASE COMMITMENTS

------------------------------------ ------------------------------------
               YEAR                         MINIMUM SLIDE PURCHASE
                                           COMMITMENT (IN MILLIONS)
------------------------------------ ------------------------------------
               1999                                  **
------------------------------------ ------------------------------------
               2000                                  **
------------------------------------ ------------------------------------
               2001                                  **
------------------------------------ ------------------------------------
               2002                                  **
------------------------------------ ------------------------------------
               2003                                  **
------------------------------------ ------------------------------------
               2004                                  **
------------------------------------ ------------------------------------
               2005                                  **
------------------------------------ ------------------------------------
               2006                                  **
------------------------------------ ------------------------------------
               2007                       See Agreement Section 5.01
------------------------------------
               2008
------------------------------------
               2009
------------------------------------
               2010
-------------------------------------------------------------------------

                                       11
<PAGE>   12

                 SCHEDULE 10 - ILLUSTRATIVE REBATE CALCULATIONS

The Estimated Rebate Payments will be calculated for each of the first three
calendar quarters using the Effective Rebate Rate, as described more fully in
sub-clause 7.03 of the Agreement. Any required adjustments will be made at the
end of the fourth calendar quarter, in accordance with sub-clause 7.03 of the
Agreement.
EXAMPLE: THE PURCHASE FORECAST FOR A GIVEN YEAR IS ** MILLION SLIDES; PRICING IS
****/SLIDE; BLENDED REBATE PERCENTAGE RATE IS ****, AS FOLLOWS:

         ********************** million slides * *** = *** million slides
         ********************** million slides * *** = *** million slides
         ********************** million slides * *** = *** million slides
         ********************** million slides * *** = *** million slides
         ********************** million slides * *** = *** million slides
         ----------------------------------------------------------------
         Total Slides Eligible for Rebate = ***** million slides

EFFECTIVE REBATE = TOTAL SLIDES ELIGIBLE FOR REBATE / TOTAL PURCHASES = ******
**********

ACTUAL VOLUME PURCHASED EQUALS VOLUME PROJECTED AT THE BEGINNING OF THE YEAR.

<TABLE>
<CAPTION>
            ------------------------------------------------------------------------------------------------------------
             Actual Qtrly.               Effective Rebate            Calculated
                 Vol.         Purchases      % (80MM                 Rebate Each       20% Holdback      Rebate Paid
              (millions)        ($MM)          Vol.)               Qtr. (millions)      (millions)       (millions)
            -------------------------------------------------------------------------------------------------------------
<S>               <C>            <C>            <C>                    <C>                  <C>               <C>
1st Qtr           **             ***            ****                   ****                 ****              ****
2nd Qtr           **            *****           ****                   ****                 ****              ****
3rd Qtr           **            *****           ****                   ****                 ****              ****
4th Qtr           **            *****           ****                   ****                 ****              ****
                  --            -----                                  ----                 ----              ----
                  **            *****                                  ****                 ****              ****
                                                         True-up:      ****                                   ****
                                                                  ---------------                        ---------------
                                                           Total:      ****                                   ****
                                                                 ================                        ================
</TABLE>

ACTUAL VOLUME PURCHASED IS GREATER THAN VOLUME PROJECTED AT THE BEGINNING OF THE
YEAR.

<TABLE>
<CAPTION>
           --------------------------------------------------------------------------------------------------------------
             Actual Qtrly.                Effective Rebate         Calculated
                 Vol.         Purchases      % (80MM               Rebate Each       20% Holdback     Rebate Paid
              (millions)        ($MM)          Vol.)             Qtr. (millions)      (millions)       (millions)
            -------------------------------------------------------------------------------------------------------------
<S>                <C>          <C>             <C>                  <C>                   <C>             <C>
1st Qtr            *            ****            ****                 ****                  ****            ****
2nd Qtr           **            *****           ****                 ****                  ****            ****
3rd Qtr           **            *****           ****                 ****                  ****            ****
4th Qtr           **            *****           ****                 ****                  ****            ****
                  --            -----                                ----                  ----            ----
                  **            *****                                ****                  ****            ****
                                                       True-up:      ****                                  ****
                                                               ----------------                      ----------------
                                                       Total:        ****                                  ****
                                                               ================                      ================
</TABLE>

                                       12
<PAGE>   13

ACTUAL VOLUME PURCHASED IS LOWER THAN VOLUME PROJECTED AT THE BEGINNING OF THE
YEAR.

<TABLE>
<CAPTION>
            -------------------------------------------------------------------------------------------------
                                             Effective       Calculated
             Actual Qtrly.                    Rebate         Rebate Each         20%
                 Vol.        Purchases       % (80MM            Qtr.          Holdback       Rebate Paid
              (millions)       ($MM)           Vol.)         (millions)      (millions)      (millions)
            -------------------------------------------------------------------------------------------------
<S>               <C>           <C>             <C>              <C>             <C>             <C>
1st Qtr           **            ****            ****             ****            ****            ****
2nd Qtr           **            *****           ****             ****            ****            ****
3rd Qtr           **            *****           ****             ****            ****            ****
4th Qtr           **            *****           ****             ****            ****            ****
                  --            -----                           ------           ----            ----
                  **            *****                            ****            ****            ****
                                                   True-up:     ******                           ****
                                                                ------                           ----
                                                     Total:      ****                            ****
                                                           ================               =================
</TABLE>

                                       13

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