1 Exhibit 21 BIOGEN, INC. Subsidiaries NAME JURISDICTION OF INCORPORATION - ---- ----------------------------- Biogen Canada, Inc. Delaware Bio Holding I, Inc. Delaware Bio Holding II, Inc. Delaware Biogen Realty Corporation Massachusetts Biogen Realty Limited Partnership Massachusetts Biogen Securities Corporation Massachusetts Biogen Technologies, Inc. Delaware Biogen Belgium S.A. Belgium Biogen B.V. The Netherlands Biogen France S.A. France Biogen GmbH Austria Biogen GmbH Germany Biogen International BV The Netherlands Biogen Limited United Kingdom Biotech Manufacturing CV The Netherlands Biotech Manufacturing Limited Channel Islands