Page 17 EXHIBIT 11 BIOGEN, INC. and SUBSIDIARIES Computation of Earnings Per Share (unaudited) (in thousands, except per share amounts) Three Months Nine Months Ended Sept. 30, Ended Sept. 30, 1997 1996 1997 1996 Primary earnings per share Weighted average number of shares outstanding . . . . . . . 74,003 71,594 73,719 71,403 Shares deemed outstanding from the assumed exercise of stock options and warrants. . . . . . 2,568 2,976 2,835 992 ------- ------- ------- ------- Total . . . . . . . . . . . . .. 76,571 74,570 76,554 72,395 ======= ======= ======= ======= Net income . . . . . . . . . . . . $20,485 $45,052 $57,443 $32,301 ======= ======= ======= ======= Primary earnings per share of common stock . . . .. . $ 0.27 $ 0.60 $ 0.75 $ 0.45 ======= ======= ======= ======= Fully diluted earnings per share (a) Weighted average number of shares outstanding. . . . . .. . 74,003 71,594 73,719 71,403 Shares deemed outstanding from the assumed exercise of stock options and warrants. . . . .. . 2,568 4,466 2,853 1,489 ------- ------- ------- ------- Total . . . . . . . . . . . . .. . 76,571 76,060 76,572 72,892 ======= ======= ======= ======= Net income . . . . . . . . . . . $20,485 $ 45,052 $57,443 $32,301 ======= ======= ======= ======= Fully diluted earnings per share of common stock . . . $ 0.27 $ 0.59 $ 0.75 $ 0.44 ======= ======= ======= ====== (a) This calculation is submitted in accordance with Regulation S-K item 601 (b) (11) although not required by Footnote 2 to Paragraph 14 of APB Opinion No. 15 because it results in dilution of less than 3%.