1 EXHIBIT 11.1 GENOME THERAPEUTICS CORP. AND SUBSIDIARIES CALCULATION OF SHARES USED IN DETERMINING PRIMARY NET INCOME (LOSS) PER SHARE YEAR ENDED AUGUST 31, ---------------------------------------- 1995 1996 1997 ---------- ---------- ---------- Weighted average common stock outstanding during the year.................................................... 12,287,918 15,530,639 17,617,614 Weighted average common stock equivalents outstanding during the year......................................... 673,816 2,599,155 -- ---------- ---------- ---------- 12,961,734 18,129,794 17,617,614 ========== ========== ========== CALCULATION OF SHARES USED IN DETERMINING FULLY DILUTED NET INCOME (LOSS) PER SHARE YEAR ENDED AUGUST 31, ---------------------------------------- 1995 1996 1997 ---------- ---------- ---------- Weighted average common stock outstanding during the year.................................................... 12,287,918 15,530,639 17,617,614 Weighted average common stock equivalents outstanding during the year......................................... 748,823 2,599,155 -- ---------- ---------- ---------- 13,036,741 18,129,794 17,617,614 ========== ========== ==========