Page 13 Exhibit 11 NATIONAL SERVICE INDUSTRIES, INC. AND SUBSIDIARIES COMPUTATIONS OF NET INCOME PER SHARE OF COMMON STOCK (In thousands, except per-share data) THREE MONTHS ENDED SIX MONTHS ENDED FEB. 28, FEB. 29, FEB. 28, FEB. 29, 1997 1996 1997 1996 Primary: Weighted Average Number of Shares (determined on a monthly basis) . 44,994 48,364 45,468 48,350 Net Income ........................ $ 20,345 $ 19,250 $ 45,179 $ 42,519 Primary Earnings per Share ........ $ .45 $ .40 $ .99 $ .88 Fully Diluted: Weighted Average Number of Shares Outstanding ..................... 44,994 48,364 45,468 48,350 Additional Shares Assuming Exercise of Options: Options exercised ............. 1,182 1,292 1,182 1,292 Treasury stock purchased with proceeds ............... (869) (1,007) (869) (983) Average Common Shares Outstanding (as adjusted) .................. 45,307 48,648 45,781 48,634 Net Income ........................ $ 20,345 $ 19,250 $ 45,179 $ 42,519 Fully Diluted Earnings per Share .. $ .45 $ .40 $ .99 $ .87