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                                                                     Exhibit 5.1


                               PALMER & DODGE LLP
                                One Beacon Street
                           Boston, Massachusetts 02018

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


                                 April 16, 1997


Genzyme Corporation
One Kendall Square
Cambridge, Massachusetts  02139


         We are rendering this opinion in connection with Registration Statement
No. 33-8881 (the "Registration Statement") relating to shares of the General
Division Common Stock, $0.01 par value, and Tissue Repair Division Common Stock,
$0.01 par value (collectively, the "Shares"), of Genzyme Corporation (the
"Company"), offered pursuant to the provisions of the Company's 1990 Equity
Incentive Plan (the "Plan").

         We have acted as your counsel in connection with the preparation of the
Registration Statement and are familiar with the proceedings taken by the
Company in connection with authorization, issuance and sale of the Shares. We
have examined all such documents as we consider necessary to enable us to render
this opinion.

         Based upon the foregoing, we are of the opinion that when issued in
accordance with the terms of the Plan and the options or other rights granted
thereunder, the Shares will be duly authorized, validly issued, fully paid and
nonassessable.

         We hereby consent to the filing of this opinion as a part of the
Registration Statement and to the reference to our firm under Item 5 thereof.


                                                     Very truly yours,


                                                     /s/ Palmer & Dodge LLP



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