Fundamental and clinical studies on cefminox (CMNX, MT-141), a new cephamycin antibiotic, were carried out and the results were as follows. After the intravenous one shot administration of 1 g CMNX to 17 cases, serum concentrations, tissue concentrations in pelvic organs and protein binding capacities in serum were measured. Blood concentrations ranged between 100-200 micrograms/immediately after the injection and declined gradually. Half-life (T1/2) was 75 minutes. Tissue concentrations were 30-70 micrograms/g (tissue weight) 10 minutes after injection and declined. Half-life was 90 minutes. The average serum protein binding rate was 66.3 +/- 8.4%. Correlation between tissue concentration (Y) and free serum concentration (X) was expressed as Y = 0.42 + 7.14X. Correlation coefficient (r) was 0.80 (r = 0.80). Correlation coefficient in serum concentrations between HPLC and bioassay was 0.83 and that in free concentration was 0.97. In clinical studies, CMNX was administered to 19 cases of obstetric and gynecological infections. The patients were constituted of 3 with puerperal endometritis, 3 with pyometra, 3 with pelvic peritonitis, 3 with parametritis, 3 with adnexitis, 2 with BARTHOLIN's abscess and 1 with retroperitoneal abscess and vulva abscess. Overall clinical efficacy was 89.5% (17/19). Bacteriologically 26 strains were isolated, 6 strains of E. coli, 4 strains of B. fragilis, 2 strains of P. anaerobius and P. asaccharolyticus and each one of E. faecalis, S. epidermidis, N. gonorrhoeae, S. marcescens, P. maltophilia, A. calcoaceticus, K. pneumoniae, P. mirabilis, H. influenzae, S. intermedius, E. lentum and F. varium. Twenty of these 24 strains were eliminated after the administration, K. pneumoniae was decreased, E. faecalis, S. marcescens and P. maltophilia remained unaffected. No side effects were observed but 1 case showed mild elevation of transaminases which normalized 1 week after CMNX was stopped.