SummaryThein vitroactivity of cefcpimc has been compared with that of cefotaxime, ceftazidime, aztreonam, and piperacillin against 1826Enterobacieriaceaeincluding 537 inducibleEnterobacieriaceae (Entero-bacterspp.,Serratiaspp.,Citrobacterspp.,Morganella morganii)and 572 non-fermenters, including 401Pseudomonas aeruginosaand 111Acinetobacterspp. isolated from hospitalized patients in 28 Belgian hospitals. Overall, ccfepime was found substantially more active than the third-generation cephalosporins, aztreonam and piperacillin againstEnterobacieriaceaespecies producing inducible type I cephalospo-rinases. Notably, cefepime remained active against 96% ofEnterobacieriaceaeresistant to cefotaxime, ceftazidime or aztreonam while it displayed a similar activity againstE. coliand the otherEnterobacieriaceae.Against non-fermenters. cefepime was found less active than ceftazidime but more than cefotaxime or aztreonam.