Cefoperazone (CPZ) has a broad antibacterial spectrum against Gram-positive, -negative aerobic and anaerobic organisms, it is also highly active against Pseudomonas sp. and Enterobacter sp. which are hardly susceptible to current cephalosporins. The clinical studies on CPZ were performed in postoperative wound infections and abdominal cavity infections, and the following results were obtained. Overall clinical effect: The rates of effectiveness were 100% in postoperative wound infections and 71.4% in abdominal cavity infections. Bacteriological effect: The rates of eradication were 90% in postoperative wound infections and 80% in abdominal cavity infections. Side effects: Any side effects on marked changes in laboratory findings were not observed in any of the cases treated with CPZ. Based on the above results, we considered that CPZ is a highly useful antibiotic for the treatment of postoperative infections.