The in vitro activity of FK-037, a novel parenteral cephalosporin, was compared to that of ceftazidime, aztreonam and piperacillin (agents often used in empiric regimens in cancer patients) against recent bacterial isolates from patients with cancer. FK-037 was either equal to or 2 to 16-fold more active than the comparative agents against members of the Enterobacteriaceae. It was also active against Acinetobacter spp., Aeromonas spp., Pseudomonas aeruginosa, and other Pseudomonas spp. Xanthomonas maltophilia and Alcaligenes denitrificans were relatively resistant to all four agents. FK-037 was also 4 to 16-fold more active against most gram-positive organisms (including some methicillin-resistant staphylococci) than was ceftazidime. Enterococcus spp., Listeria monocytogenes and Staphylococcus haemolyticus were relatively resistant to FK-037 and ceftazidime. Overall, FK-037 has a broad antimicrobial spectrum that includes the majority of gram-positive and gram-negative isolates.