Biogen Idec Names Paul J. Clancy Chief Financial Officer

Biogen Idec (NASDAQ: BIIB) announced today that Paul Clancy has
been appointed Executive Vice President and Chief Financial Officer,
effective August 13, 2007. He reports directly to James C. Mullen, the
company's Chief Executive Officer.

"Paul brings more than 20 years of experience in financial
management and strategic business planning," Mullen said, "In his six
years at Biogen Idec, he has repeatedly proven himself to be an
effective and valued leader. With Paul's help, we will continue to
optimize shareholder value by driving our strategic and operational
plans."

Clancy is currently Senior Vice President of Finance, with
responsibilities for leading the Treasury, Tax, Investor Relations and
Business Planning groups. He has held several senior executive
positions since joining the company in 2001, including Vice President
of Business Planning, Portfolio Management and US Marketing. Prior to
joining the company, he spent 13 years at PepsiCo, serving in a range
of financial and general management positions.

Clancy received his MBA from Columbia Business School in New York
City and his BS in Business Administration at Babson College in
Wellesley, MA.

About Biogen Idec

Biogen Idec creates new standards of care in therapeutic areas
with high unmet medical needs. Founded in 1978, Biogen Idec is a
global leader in the discovery, development, manufacturing, and
commercialization of innovative therapies. Patients in more than 90
countries benefit from Biogen Idec's significant products that address
diseases such as lymphoma, multiple sclerosis, and rheumatoid
arthritis. For product labeling, press releases and additional
information about the company, please visit www.biogenidec.com.

Safe Harbor

This press release contains forward-looking statements in the
comments from James Mullen, our CEO. Forward-looking statements are
subject to risks and uncertainties that could cause actual results to
differ materially from that which we expect. Important factors that
could cause our actual results to differ are described in our most
recent Form 10-Q filing with the SEC. These forward-looking statements
speak only as of the date of this press release, and we do not
undertake any obligation to publicly update any forward-looking
statements, whether as a result of new information, future events or
otherwise.