Cefetamet pivoxil is a new beta lactamase orally stable administered cephalosporin. Antimicrobial resistance among respiratory pathogens has become an important problem for both the physician and the microbiologist and the patterns of resistance vary greatly depending on geographic location, often requiring in vitro susceptibility testing of isolates. OBJECTIVE The in vitro activity of cefetamet, the microbiologically active metabolite of the prodrug cefetamet pivoxil, was compared with other 11 drugs against 376 bacterial strains recently isolated from patients with respiratory tract infections. METHODS The comparative activity in vitro of cefetamet and other 11 antimicrobial agents was measured against 376 bacterial strains isolated from patients with respiratory tract infections, during a six month period. Through the determination of minimum inhibitory concentration by the microdilution technique, patterns of antimicrobial resistance were reported. RESULTS Cefetamet showed high in vitro activity against all the bacterial tested, possessing a spectrum of activity similar to that other recently developed oral cephalosporins. The good activity of cefetamet against beta-lactamase producing isolates, like Moraxella catarrhalis, can be due to its beta-lactamase stability. At a concentration of 1.0 microgram/mL, cefetamet inhibited 97% of all the tested bacteria. CONCLUSIONS The MIC90 of the cumulative susceptibility results of the 12 antimicrobics tested in the 376 strains studied, confirm the excellent activity of cefetamet against the common respiratory tract pathogens.