Fact Sheets		SEC Filing		Literature Request
	Financial News		Cost Basis

Stockholder Advisory for Exchanged Holders of Genzyme Biosurgery Common Stock and Genzyme Molecular Oncology Common Stock

On June 30, 2003, Genzyme Corporation completed the exercise of options under its corporate charter to exchange the outstanding stock of Genzyme Biosurgery and Genzyme Molecular Oncology for Genzyme General common stock. The following information is provided to assist stockholders in determining what their adjusted tax basis should be following the exchange of their respective shares into Genzyme common stock.

This information is a general summary. Your own federal income tax consequences will depend on your individual tax situation and may differ from those described here. For example, special rules may apply to you if you acquired your Genzyme Biosurgery or Molecular Oncology shares at different times for different prices or upon exercise of an employee stock option. This summary does not address state or local tax consequences. As part of the tax-free recapitalization, you will need to attach a statement to your individual tax return describing this transaction. Genzyme will prepare a statement (with instructions) in January 2004 and will make it available for stockholders use to attach to their tax returns. The information required to be disclosed by stockholders is found in Treas. Reg. 1.368-3(b).

Holders of Genzyme Biosurgery Division Common Stock

Determining Your Tax Basis. For each share of Genzyme Biosurgery stock that you owned, you received 0.04914 of a share of Genzyme General stock. To determine the tax basis for your Genzyme General shares, you will need to know your tax basis in your Genzyme Biosurgery stock. This figure may be obtained from bank or brokerage statements, inheritance or gift records, or your own personal records. Your aggregate tax basis for your Genzyme General shares will equal your tax basis for your Genzyme Biosurgery stock, less the portion of that tax basis that is allocated to any fractional share for which you received cash.

Treatment of Fractional Shares. You received cash in lieu of any fractional share of Genzyme General stock into which your Genzyme Biosurgery stock converted, at a rate of $45.41 per share of Genzyme General stock. This cash will be treated for federal income tax purposes as paid in redemption of the fractional share. Provided the fractional share is treated as a capital asset, you realized gain or loss on this deemed redemption measured by the difference between the cash received for the fractional share and your tax basis for the fractional share.

Example. Suppose you owned 600 shares of Genzyme Biosurgery stock which you purchased for $8.00 per share. Your tax basis in your Genzyme Biosurgery stock would be $4,800.00. Consequently, your tax basis per share for the whole shares of Genzyme General stock that you

received and your gain or loss on the cash you received in lieu of a fractional share of Genzyme General stock would be as follows:

a.	Tax basis of Genzyme Biosurgery stock = $4,800
b.	Total shares of Genzyme General stock = 600 x 0.04914 = 29.484
c.	Tax basis per share of Genzyme General stock (line a/line b) = $4,800/29.484 = $162.80
d.	Cash received for fractional share = $45.41 x .484 = $21.98
e.	Tax basis allocated to fractional share = $162.80 x .484 = $78.80
f.	Loss on cash received for fractional share = $21.98 - $78.80 = ($56.82)

Holders of Genzyme Molecular Oncology Division Common Stock

Determining Your Tax Basis. For each share of Genzyme Molecular Oncology stock that you owned, you received 0.05653 of a share of Genzyme General stock. To determine the tax basis for your Genzyme General shares, you will need to know your tax basis in your Genzyme Molecular Oncology stock. This figure may be obtained from bank or brokerage statements, inheritance or gift records, or your own personal records. Your aggregate tax basis for your Genzyme General shares will equal your tax basis for your Genzyme Molecular Oncology stock, less the portion of that tax basis that is allocated to any fractional share for which you received cash.

Treatment of Fractional Shares. You received cash in lieu of any fractional share of Genzyme General stock into which your Genzyme Molecular Oncology stock converted, at a rate of $45.41 per share of Genzyme General stock. This cash will be treated for federal income tax purposes as paid in redemption of the fractional share. Provided the fractional share is treated as a capital asset, you realized gain or loss on this deemed redemption measured by the difference between the cash received for the fractional share and your tax basis for the fractional share.

Example. Suppose you owned 800 shares of Genzyme Molecular Oncology stock which you purchased for $2.00 per share. Your tax basis in your Genzyme Molecular Oncology stock would be $1,600.00. Consequently, your tax basis per share for the whole shares of Genzyme General stock that you received and your gain or loss on the cash you received in lieu of a fractional share of Genzyme General stock would be as follows:

a.	Tax basis of Genzyme Molecular Oncology stock = $1,600
b.	Total shares of Genzyme General stock = 800 x 0.05653 = 45.224
c.	Tax basis per share of Genzyme General stock (line a/line b) = $1,600/45.224 = $35.38
d.	Tax basis allocated to fractional share = $35.38 x .224 = $7.93
e.	Cash received for fractional share = $45.41 x .224 = $10.17
f.	Gain on cash received for fractional share = $10.17 - $7.93 = $2.24

Because the tax consequences of the exchange may vary depending upon your particular circumstances, we urge you to consult your own tax advisors about the federal, state, local or foreign tax consequences this transaction will have on you.

Genzyme Shareholder Relations

(617) 252-7526

Terms and Conditions of Use | Privacy Policy | © 2002-2009 Genzyme Corporation. All rights reserved.