We conducted clinical studies on the efficacy and safety of cefbuperazone (CBPZ) on surgical infections with the following results. 1) In evaluable 32 patients, CBPZ was evaluated to be clinically effective in 23 (71.9%) and the efficacy rate was better in those who were administered 4 g/day of CBPZ (87.5%, 14/16) than in those who were given 2 g/day (57.1%, 8/14). 2) Antibacterial activity of CBPZ was evaluated in 41 isolated bacterial strains. Pathogen eradication rate by bacterial species was 75.6% (31/41). CBPZ exerted excellent antibacterial effects on Escherichia coli (100%, 8/8) and anaerobic bacteria such as Bacteroides (88.9%, 8/9). Resistant bacteria to CBPZ were Enterococcus faecalis and Pseudomonas aeruginosa. 3) No serious side effects were noted in any of the 34 patients who entered in this study. Abnormal laboratory test results were noted in 2 patients (5.9%) and they were transient elevation of transaminases and alkaline phosphatase. From the results shown above, CBPZ appears to be a highly useful antibiotic for the treatment of surgical infection.