Cefepime is a new aminothiazolylacetamido cephalosporin with a wider spectrum and greater potency than many currently available cephalosporins. It appears that these characteristics result from multiple properties of the molecule. In contrast to older cephalosporins, cefepime more rapidly penetrates the gram-negative cell, targets multiple essential penicillin-binding proteins, and escapes the effects of many beta-lactamases due to the enzymes' low affinity for the drug. The latter characteristic is most apparent in studies of Bush group 1 beta-lactamases. Derepression of this class of beta-lactamases has less effect on the in vitro activity of cefepime than on that of other cephalosporins. The results of clinical trials should now be carefully analyzed to determine whether these advantages carry over into the clinical arena.