Exhibit 21
BIOGEN IDEC INC.
The following is a list of subsidiaries of Biogen Idec Inc. as of December 31, 2011, omitting some subsidiaries which, considered in the aggregate, would not constitute a significant subsidiary.
| SUBSIDIARY |
STATE OR OTHER JURISDICTION OF INCORPORATION OR ORGANIZATION | |
| Biogen Idec MA Inc. |
Massachusetts | |
| Biogen Idec New Ventures, Inc. |
Delaware | |
| Biogen Idec Manufacturing Holding LLC |
Delaware | |
| Biogen Idec Holding I Inc. |
Delaware | |
| Biogen Idec Holding II Inc. |
Delaware | |
| Biogen Idec Realty Corporation |
Massachusetts | |
| Biogen Idec Realty Limited Partnership |
Massachusetts | |
| Biogen Idec U.S. Corporation |
Massachusetts | |
| Biogen Idec U.S. Limited Partnership |
Massachusetts | |
| Biogen Idec (RTP) Realty LLC |
Delaware | |
| The Biogen Idec Foundation Inc. |
Massachusetts | |
| Biogen Idec U.S. Pacific LLC |
Delaware | |
| Biogen Idec U.S. West Corporation |
Delaware | |
| Biogen Idec Therapeutics Inc. |
Delaware | |
| Biogen Idec Nobel Research Center, LLC |
Delaware | |
| Conforma Therapeutics Corporation |
Delaware | |
| Biogen Idec Hemophilia Inc. |
Delaware | |
| Biogen Idec Canada Inc. |
Delaware | |
| Biogen Idec SRO, Inc. |
Delaware | |
| Biogen Idec (Argentina) SRL |
Argentina | |
| Biogen Idec Australia PTY Ltd |
Australia | |
| Biogen Idec Austria GmbH |
Austria | |
| Biogen Idec Belgium N.V./S.A. |
Belgium | |
| Biogen Idec Brazil Produtos Farmaceuticos LTDA |
Brazil | |
| Biogen Idec (Czech Republic) s.r.o. |
Czech Republic | |
| Biogen Idec (Denmark) A/S |
Denmark | |
| Biogen Idec (Denmark) Manufacturing ApS |
Denmark | |
| Biogen Idec Holding APS |
Denmark | |
| Biogen Idec Finland OY |
Finland | |
| Biogen Idec France S.A.S. |
France | |
| Biogen Idec GmbH |
Germany | |
| Biogen Idec Biotech India Pvt. Ltd. |
India | |
| Biogen Idec (Ireland) Ltd. |
Ireland | |
| Biogen Idec Japan Ltd. |
Japan | |
| Biogen Idec Mexico S. DE R.L. DE C.V. |
Mexico | |
| Biogen Idec B.V. |
The Netherlands | |
| Biogen Idec International B.V. |
The Netherlands | |
| Biogen Idec Norway AS |
Norway | |
| Biogen Idec NZ Ltd. |
New Zealand | |
| Biogen Idec Portugal Sociedade Farmaceutica, Unipessoal, Lda. |
Portugal | |
| Biogen Idec Iberia, S.L. |
Spain | |
| Biogen Idec (Slovak Republic) s.r.o. |
Slovak Republic | |
| Biogen Idec promet s farmacevtskimi in biotehnoloskimi proizvodi d.o.o |
Slovenia | |
| Biogen Idec Sweden AB |
Sweden | |
| Biogen Idec International GmbH |
Switzerland | |
| Eidetica Biopharma GmbH |
Switzerland | |
| Biogen Idec Ltd. |
UK | |
| Biogen Idec Switzerland AG |
Switzerland | |
| Biogen Idec Italia SRL |
Italy | |
| Biogen Idec Luxembourg Holding SARL |
Luxembourg | |
| Biogen Idec International Holding Limited |
Bermuda | |
| Arrowpark Interseas Ltd |
Isle of Man | |
| Wolter Interseas Ltd |
Isle of Man |
| Biogen Idec Management Services GmbH |
Switzerland | |
| Biogen Idec (Denmark) New Manufacturing ApS |
Denmark | |
| Fundacion Biogen Idec |
Spain | |
| Biogen Idec (Hong Kong) Limited |
Hong Kong | |
| Biogen Idec (Singapore) Pte Ltd |
Singapore | |
| Biogen Idec Hungary KFT |
Hungary | |
| Biogen Idec Uruguay SA |
Uruguay | |
| Biogen Idec Chile Spa |
Chile | |
| Biogen Idec International Neuroscience GmbH |
Switzerland | |
| Biogen Idec Poland |
Poland | |
| Biogen Idec Pharmaceutical Consultancy (Shanghai) Co., Ltd. |
China | |
| Biogen Idec Research Ltd. |
UK |