Exhibit 5
                               PALMER & DODGE LLP
                   111 Huntington Avenue, Boston, MA 02199

Telephone:  (617) 239-0100                            Facsimile:  (617) 227-4420


                                January 15, 2002


Genzyme Corporation
One Kendall Square
Cambridge, Massachusetts  02139


         We are rendering this opinion in connection with the registration
statement on Form S-8 (the "Registration Statement") filed by Genzyme
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 250,000 shares of Genzyme General Division
common stock, $0.01 par value, 200,000 shares of Genzyme Biosurgery Division
common stock, $0.01 par value, and 150,000 shares of Genzyme Molecular Oncology
Division common stock, $0.01 par value (collectively, the "Shares"), offered
pursuant to the provisions of the Company's 1998 Director Stock Option 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, 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.

                                            Very truly yours,

                                            /s/ Palmer & Dodge LLP

                                            Palmer & Dodge LLP