Exhibit 5.1

     IDEXX                                            IDEXX Laboratories, Inc.
                                   One IDEXX Drive, Westbrook, Maine 04092 USA
                                                        Telephone 207-856-0300
     August 30, 1996                                    Facsimile 207-856-0346
                                                              Telex 9103807069

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

          Re:  1991 Stock Option Plan

     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-8 (the
     "Registration Statement") to be filed with the Securities and
     Exchange Commission relating to the registration of 975,000
     shares of Common Stock, par value $.10 per share (the "Shares"),
     of the Company, issuable upon exercise of options to be granted
     under the Company's 1991 Stock Option Plan (the "Plan").

          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 to be issued under the Plans, as described
     in the Registration Statement, and the Shares, when issued in
     accordance with the terms of the Plan, will be 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
                                        Richard B. Thorp
                                        General Counsel