Exhibit 11 ENGINEERED SUPPORT SYSTEMS, INC. STATEMENT RE: COMPUTATION OF EARNINGS PER SHARE (in thousands, except per share amounts) Three Months Ended January 31 --------------------- 2005 2004 ---- ---- NET INCOME $20,611 $15,743 ======= ======= BASIC EARNINGS PER SHARE: Average basic shares outstanding 26,827 25,066 ======= ======= Basic earnings per share $ 0.77 $ 0.63 ======= ======= DILUTED EARNINGS PER SHARE: Average basic shares outstanding 26,827 25,066 Net effect of dilutive stock options (1) 1,521 2,486 ------- ------- Total 28,348 27,552 ======= ======= Diluted earnings per share $ 0.73 $ 0.57 ======= ======= <FN> (1) Based on the treasury stock method.