1 CONSENT OF INDEPENDENT ACCOUNTANTS We hereby consent to the incorporation by reference in the Registration Statements on Form S-3, as amended (Nos. 33-14741, 33-14743, 33-20183, 33-51639, and 333-71695) and in the Registration Statements on Form S-8, as amended (Nos. 2-87550, 2-96157, 33-9827, 33-14742, 33-37312, 33-22378, 33-41077, 33-69174, 33-63013, 33-63015, 333-42887, and 333-70701) of Biogen, Inc. and its subsidiaries of our report dated January 14, 2000 appearing in the 1999 Annual Report to Shareholders which is incorporated in this Annual Report on Form 10-K. We also consent to the incorporation by reference of our report on the Financial Statement Schedule, which appears in this Annual Report on Form 10-K. PricewaterhouseCoopers LLP Boston, Massachusetts March 28, 2000