Telephone: (617) 573-0100                              Facsimile: (617) 227-4420

                                                                       Exhibit 5

                                November 29, 2000

Genzyme Transgenics Corporation
175 Crossing Boulevard, Suite 410
Framingham, MA  01702-9322

Ladies and Gentlemen:

         We are rendering this opinion in connection with the Registration
Statement on Form S-3 (the "Registration Statement") filed by Genzyme
Transgenics Corporation (the "Company") with the Securities and Exchange
Commission under the Securities Act of 1933, as amended, on or about the date
hereof. The Registration Statement relates to 333,334 shares of the Company's
common stock, $0.01 par value per share (the "Shares"), proposed to be sold by
the selling stockholders named in the Registration Statement. We understand that
the Shares are to be offered and sold in the manner described in the
Registration Statement.

         We have acted as your counsel in connection with the preparation of the
Registration Statement. We are familiar with the proceedings of the Board of
Directors in connection with the authorization, issuance and sale of the Shares.
We have examined such other documents as we consider necessary to render this
opinion.

          Based upon the foregoing, we are of the opinion that the Shares have
been duly authorized and are validly issued, fully paid and non-assessable.

         We hereby consent to the filing of this opinion as a part of the
Registration Statement and to the reference to our firm under the caption "Legal
Matters" in the Prospectus filed as part thereof.

                                very truly yours,

                               /s/ PALMER & DODGE LLP

                               PALMER & DODGE LLP