Biogen Idec is headquartered in Kendall Square in Cambridge, Massachusetts, and operates research and development facilities in Cambridge and San Diego. Biogen Idec operates a manufacturing facility in Research Triangle Park, North Carolina. The company employs about 4,000 people.
Biogen Idec's principal competitors include Genentech (with which the company has a marketing partnership for the cancer drug Rituxan), Amgen, Serono, and Elan Pharmaceuticals. As of 2003, Biogen Idec derives most of its income from sales of multiple sclerosis treatment Avonex and partnership royalties on Rituxan.