The in vitro activity of FK-037, a novel parenteral oxime-type cephalosporin, was compared with that of cefepime, cefpirome, ceftazidime, imipenem, and gentamicin against a total of 668 recent clinical isolates. Minimum inhibitory concentrations were determined by a standard agar dilution procedure, and all isolates were tested at two inocula (10(4) and 10(6) colony forming units). FK-037 inhibited 90% of isolates of Escherichia coli, Klebsiella species, Proteus mirabilis, P. vulgaris, Morganella morganii, Serratia marcescens, Providencia stuartii, Citrobacter freundii, Salmonella typhi, Shigella sonnei, Yersinia enterocolitica, Aeromonas species, and Haemophilus influenzae at < or = 1 microgram/ml. FK-037 was less active against Enterobacter species, Acinetobacter species, and Pseudomonas species, requiring 16 micrograms/ml to inhibit 90% of isolates, and was inactive against Xanthomonas maltophilia. FK-037 inhibited 90% of methicillin-susceptible Staphylococcus aureus at < or = 1 microgram/ml and 90% of methicillin-resistant S. aureus at < or = 8 micrograms/ml.