Purpose and Effective Date. The purpose of this plan is to provide certain key executives and
managers of Biogen Idec (or its subsidiaries) with additional tax-deferred savings opportunities
supplementing those available under the Savings Plan. This plan allows certain eligible
participants to make voluntary deferrals from base salary or bonus if elected by a participant. In
addition, certain participants whose compensation exceeds the Code Section 401(a)(17) limit
applicable to the Savings Plan will receive an employer 401(k) restoration credit in accordance
with Section 4.1, and certain participants received transition credits in accordance with Section
This plan also contains certain account balances or benefits previously maintained under the
amended and restated IDEC Pharmaceuticals Corporation Deferred Compensation Plan, the Biogen, Inc.
Voluntary Executive Supplemental Savings Plan, and the Biogen, Inc. Supplemental Executive
This amended and restated plan document is effective as of January 1, 2005, except as
otherwise specified. Certain historical information about the plan and any amendments thereto is
set forth in Appendix A.