Therapeutic effects of intravenously administered cefpirome on experimental bacterial infections in croton oil-induced rat granuloma pouches were compared with those of ceftazidime, moxalactam, cefoperazone, and cefotaxime. Its pharmacokinetic profile in pouch exudate was also examined. Cefpirome showed bactericidal effects and long-lasting bacterial growth-inhibitory effects in granuloma pouches infected in Escherichia coli Ec-7, and its effects were almost equal to those of the other antibiotics. Against Pseudomonas aeruginosa TM-11 infection, cefpirome was more active than moxalactam, cefoperazone, and cefotaxime and comparable to ceftazidime. Cefpirome had the strongest activity against Staphylococcus aureus Smith infection among the five antibiotics, showing bactericidal effects and long-lasting bacterial growth-inhibitory effects. The level of cefpirome in pouch exudate peaked at 1 h after administration, with a value of 16.4 micrograms/ml, and declined in a pattern similar to that of ceftazidime. When compared in peak level, the exudate level of cefpirome was 1.8 to 2.6 times higher than the values of moxalactam, cefoperazone, and cefotaxime. The in vitro exudate protein binding of cefpirome was 8.8%, which was the lowest among the antibiotics used.