Cefmetazole is a new semisynthetic derivative with a broad antibacterial spectrum as shown by data from 34 research institutes in Japan. It has antibacterial action against various species of Gram+ and Gram- bacteria and is extremely stable for beta-lactamase because it has a 7-alpha-methoxy group. In addition, it has excellent antibacterial activity against indole-positive Proteus strains against which conventional Cephalosporins are ineffective. Results of clinical trials carried out on urinary tract, respiratory tract and cutaneous infections are reported. A total of 30 patients were examined; the route of administration was intravenous, the most frequent daily-dose was 2 g. Clinical and bacteriological effectiveness of cefmetazole was 80% with excellent activity against E. coli, Proteus, S. aureus and K. pneumoniae. No serious side effect was observed. The above results indicate that CMZ is largely effective and useful for infections due to Gram+ cocci and Gram- bacilli.