We studied the in vitro activity of cefminox (MIC by agar dilution) and cefoxitin against 477 facultative Gram-positive and Gram-negative isolates which were recovered from clinical specimens and identified by standard methods. Cefminox has proved to be 4-16 times more active than cefoxitin against enteric Gram-negative bacilli commonly involved in cholecystitis, secondary peritonitis, intraabdominal abscesses and gynecological infections. On the contrary, cefoxitin has proved to be four times more active against Gram-positive cocci. Both have been ineffective against Enterobacter spp., Pseudomonas aeruginosa and Acinetobacter spp. The microbiological activity and pharmacokinetic parameters of cefminox make it one of the first choice treatments for community-acquired intraabdominal and pelvic infections with the presence of anaerobes.