The in vitro activity of E-0702 was compared with the in vitro activity of cefotaxime, ceftazidime, moxalactam, and aztreonam against 600 gram-positive and gram-negative aerobic and anaerobic isolates. E-0702 had a minimal inhibitory concentration for 50% of isolates (MIC50) of 25 micrograms for Staphylococcus aureus, 50 micrograms for Staphylococcus epidermidis, and 1.6 to 3.1 micrograms for streptococci, with Streptococcus faecalis resistant. E-0702 had MIC50s against Escherichia coli, Klebsiella pneumoniae, and Enterobacter aerogenes comparable to those of cefotaxime, ceftazidime, moxalactam, and aztreonam, but MIC90S were higher than those of the other agents. It was as active as the other agents against Proteus mirabilis, Salmonella spp., and Shigella spp., but was four- to eightfold less active against Citrobacter freundii, Enterobacter cloacae, Providencia spp., Morganella spp., and Proteus vulgaris, with isolates in each species resistant. Activity against Bacteroides fragilis was fourfold less than that of cefoxitin. E-0702 was hydrolyzed by plasmid beta-lactamases and was only a weak inhibitor of plasmid and chromosomal beta-lactamases. There was an inoculum effect for E. cloacae, Serratia spp., Morganella spp., and Pseudomonas spp.