Vest Type

Exhibit 10.15.1

Effective                                   , you have been granted a(n) Incentive Stock Option to buy                 shares of GENZYME CORPORATION (the Company) stock at $                per share.

The total option price of the shares granted is $               .

Shares in each period will become fully vested on the date shown.

MAINTAIN THIS COPY FOR YOUR RECORDS.

These options are granted under and governed by the terms and conditions of the Company’s Stock Option plan as amended and the Option Agreement, all of which are attached and made a part of this document.

GENZYME CORPORATION 2004 EQUITY INCENTIVE PLAN

Officer (Tier I/II)

Incentive Stock Option Terms And Conditions

1.  Plan Incorporated by Reference. This Stock Option is issued pursuant to the terms of the Plan and may be amended as provided in the Plan. Capitalized terms used and not otherwise defined in this certificate have the meanings given to them in the Plan. This certificate does not set forth all of the terms and conditions of the Plan, which are incorporated herein by reference. Copies of the Plan may be obtained upon written request without charge from the Shareholder Relations Department of the Company.

2.  Option Price. The price to be paid for each share of Stock issued upon exercise of the whole or any part of this Stock Option is the option price set forth on the face of this certificate (the “Option Price”).

3.  Exercisability Schedule. This Stock Option may be exercised at any time and from time to time up to the number of shares and in accordance with the exercisability schedule set forth on the face of this certificate, but only for the purchase of whole shares. This Stock Option may not be exercised as to any shares after the date of expiration set forth on the face of this certificate (the “Expiration Date”).

4.  Method of Exercise. To exercise this Stock Option, the Participant shall deliver written notice of exercise to the Company specifying the number of shares with respect to which the Stock Option is being exercised accompanied by payment of the Option Price for such shares in cash, by certified check or in such other form, including shares of Stock of the Company valued at their Fair Market Value on the date of delivery, as the Administrator may approve. Promptly following such notice, the Company will deliver to the Participant a certificate representing the number of shares with respect to which the Stock Option is being exercised.

5.  Recapitalization, Mergers, Etc. In the event of a Covered Transaction, the Administrator may upon written notice to the Participant provide that this Stock Option shall terminate on a date not less than 20 days after the date of such notice unless theretofore exercised. In connection with such notice, the Administrator may in its discretion accelerate or waive any deferred exercise period.  Notwithstanding the foregoing, in the event of a change in control of the Company (as defined in a vote of the Compensation Committee adopted May 29, 2002), this Stock Option shall become exercisable as to all shares without regard to any deferred exercisability schedule or deferred exercise period.

6.  Stock Option Not Transferable. This Stock Option is not transferable by the Participant otherwise than by will or the laws of descent and distribution, and is exercisable, during the Participant’s lifetime, only by the Participant. The naming of a Designated Beneficiary does not constitute a transfer. A “Designated Beneficiary” means the beneficiary designated by the Participant, in a manner determined by the Administrator, to receive amounts due or exercise rights of the Participant in the event of the Participant’s death.  In the absence of an effective designation by the Participant, “Designated Beneficiary” means the Participant’s estate.

7.  Exercise of Stock Option After Termination of Employment. If the Participant’s employment with (a) the Company, (b) an Affiliate, or (c) a corporation (or parent or subsidiary corporation of such corporation) issuing or assuming a stock option in a transaction to which section 424(a) of the Code applies, is terminated for any reason other than by disability (within the meaning of section 22(e)(3) of the Code) death or retirement, the Participant may exercise the rights which were available to the Participant at the time of such termination only within three months from the date of termination. If Participant’s employment is terminated as a result of disability, such rights may be exercised within twelve months from the date of termination.  If Participant’s employment is terminated as a result of retirement (which is defined as a minimum of age 60 plus a minimum of five years of service provided employment is not terminated for cause), this Stock Option shall become

exercisable as to all shares without regard to any deferred exercise period, and such rights may be exercised within three years from the date of termination.  Upon the death of the Participant, his or her Designated Beneficiary shall have the right, at any time within twelve months after the date of death, to exercise in whole or in part any rights that were available to the Participant at the time of death.  If the Participant’s employment is terminated for cause, the Participant may exercise the rights which were available to the Participant at the time of such termination only within three months from the date of termination.  Termination by the Company of the Participant’s employment for “cause” shall mean termination upon (A) the willful and continued failure by him or her to substantially perform his or her duties with the Company (other than any such failure resulting from his or her incapacity due to physical or mental illness) after a written demand for substantial performance is delivered to the Participant by the Company, which demand specifically identifies the manner in which the Company believes that he or she has not substantially performed his or her duties, or (B) the willful engaging by the Participant in conduct which is demonstrably and materially injurious to the Company, monetarily or otherwise.  No act, or failure to act, on the Participant’s part shall be deemed “willful” unless done, or omitted to be done, by him or her not in good faith and without reasonable belief that his or her action or omission was in the best interest of the Company.  In the case of any Participant who is a corporate officer of the Company, determination for purposes of this section of whether termination of such Participant’s employment is for “cause” shall be made by the Committee.  In the case of any Participant who is not a corporate officer of the Company, determination for purposes of this section of whether termination of such Participant’s employment is for “cause” shall be made by the Senior Vice President, Chief Human Resources Officer, in his sole discretion, whose decision shall be final. Notwithstanding any of the foregoing, no rights under this Stock Option may be exercised after the Expiration Date.

8.  Payment of Taxes. The Participant shall pay to the Company, or make provision satisfactory to the Company for payment of any taxes required by law to be withheld with respect to the exercise of this Stock Option. The Administrator may, in its discretion, require any other federal or state taxes imposed on the sale of the shares to be paid by the Participant.  In the Administrator’s discretion, such tax obligations may be paid in whole or in part in shares of Stock, including shares retained from the exercise of this Stock Option, valued at their Fair Market Value on the date of delivery.  The Company and its Affiliates may, to the extent permitted by law, deduct any such tax obligations from any payment of any kind otherwise due to the Participant.

9. Notice of Sale of Shares Required.  The Participant agrees to notify the Company in writing within 30 days of the disposition of any shares purchased upon exercise of this Stock Option if such disposition occurs within two years of the date of the grant of this Stock Option or within one year after such purchase.

10. Rights Limited.  The Administrator, in its sole discretion, shall determine from the group of eligible persons whether an individual shall be a Participant under the Plan.  Any grant made under the Plan shall be made in the sole discretion of the Administrator and no prior grant shall entitle a person to any future grant.  Nothing in the Plan or any Stock Option grant will be construed as giving any person the right to continued employment or service with the Company or its Affiliates, or any rights as a shareholder except as to shares of Stock actually issued under the Plan.  In no event shall the Plan, or any grant made under the Plan, form a part of an employee’s or consultant’s contract of employment or service, if any.  The loss of existing or potential profit in Stock Options will not constitute an element of damages in the event of termination of employment or service for any reason, even if the termination is in violation of an obligation of the Company or Affiliate to the Participant.

11.  Acceptance.  Failure of the Participant to accept the terms and conditions of this Stock Option in accordance with the requirements of the Administrator can result in adverse consequences to the Participant, including cancellation of the Stock Option.