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                                                                       EXHIBIT 5
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                               September 19, 1997


IDEXX Laboratories, Inc.
One IDEXX Drive
Westbrook, Maine  04092

          Re:       Registration Statement on Form S-3 relating to 5,894 shares
                    of the common stock, $.10 par value, of IDEXX LABORATORIES,
                    INC. (THE "REGISTRATION STATEMENT")
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Ladies and Gentlemen:

     I am General Counsel to IDEXX Laboratories, Inc., a Delaware corporation
(the "Company"). In such capacity, I have assisted in the preparation of a
Registration Statement on Form S-3 (the "Registration Statement") to be filed
with the Securities and Exchange Commission relating to the re-sale of 5,894
shares of common stock, par value $.10 per share (the "Shares"), of the Company,
by a Stockholder of the Company.

     I have examined the Restated Certificate of Incorporation of the Company,
as amended, the Amended and Restated By-Laws of the Company, as amended, and
originals, or copies certified to my satisfaction, of all pertinent records of
the meetings of the directors and stockholders of the Company, the Registration
Statement and such other documents relating to the Company as I have deemed
material for purposes of this opinion.

     In my examination of the foregoing documents, I have assumed the
genuineness of all signatures and the authenticity of all documents submitted to
me as originals, the conformity to original documents of all documents submitted
to me as certified or photostatic copies, and the authenticity of the originals
of such latter documents.

     Based on the foregoing, I am of the opinion that the Company has duly
authorized for issuance the shares covered by the Registration Statement, and
that the shares are legally issued, fully paid and nonassessable.

     I hereby consent to the filing of this opinion with the Securities and
Exchange Commission in connection with the Registration Statement.

                                Very truly yours,

                               /s/ Richard B. Thorp
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                               Richard B. Thorp
                               General Counsel