Cefmetazole (CMZ) was applied to the subjects with infectious skin disease of more than middle severe cases in the present study, and the following results were obtained. 1. The clinical effects were as follows: among 15 clinical cases, 1 remarkably effective and 14 effective cases were observed, with 100% of effectiveness. 2. Bacteriological effects were as follows: 11 strains of S. aureus and 4 strains of S. epidermidis were isolated and all of them disappeared by the administration of CMZ. 3. Sensitivity test using a disc method showed that good sensitivity of better than (++) was obtained by CMZ and CEZ for all tested bacteria. 4. CMZ showed excellent clinical effects on the subjects to which oral cephalosporins and penicillins were not effective. 5. No undesirable side effects ascribable to the CMZ administration were observed.