1 Page 24 Exhibit 11 NATIONAL SERVICE INDUSTRIES, INC. AND SUBSIDIARIES COMPUTATIONS OF NET INCOME PER SHARE OF COMMON STOCK (In thousands, except per-share data) Years Ended August 31 -------------------------------------------------- 1997 1996 1995 ------------- ------------- ----------- Primary: Weighted Average Number of Shares (determined on a monthly basis) 45,191 47,941 48,696 ============ ============ ========== Net Income $ 107,278 $ 101,148 $ 94,097 ============ ============ ========== Primary earnings per Share $ 2.37 $ 2.11 $ 1.93 ============ ============ ========== Fully Diluted: Weighted Average Number of Shares Outstanding 45,191 47,941 48,696 Additional Shares Assuming Exercise of Options: Options exercised 1,379 1,260 989 Treasury stock purchased with proceeds (952) (919) (835) ------------ ------------- ---------- Average Common Shares Outstanding (as adjusted) 45,618 48,282 48,850 ============ ============= ========== Net Income $ 107,278 $ 101,148 $ 94,097 ============ ============= ========== Fully Diluted Earnings per Share $ 2.35 $ 2.09 $ 1.93 ============ ============= ==========