Cefminox (CMNX, MT-141), a new cephamycin antibiotic, was studied both fundamentally and clinically with following results. In 33 cases undergone total hysterectomy and adnexectomy, 1 g of CMNX was administered intravenously by the drip infusion route over 1 hour and changes in drug concentration in the venous blood and uterine arterial blood as well as in various uterine tissues including endometrium, myometrium, cervix uteri, portio vaginalis, oviduct and ovary were studied. In addition, in 3 cases also received 1 g of CMNX over 1 hour by the drip infusion route, changes in the concentration of CMNX in the pelvic dead space exudate were investigated. In each tissue studied, the drug concentration higher than 40 micrograms/g was attained at 20 minutes after completion of drip infusion, showing good transfer of CMNX. In the pelvic dead space exudate, the peak concentration of 24.7 micrograms/ml appeared at 4 hours after completion of drip infusion and at 12 hours still a concentration of 4.5 micrograms/ml was maintained. In the treatment of 15 cases of obstetrical and gynecological infections, CMNX was used. In all of the cases treated, clinical results better than good were obtained, with excellent results in 2 cases and good results in 13 cases. In none of the cases side effects or laboratory abnormalities were observed. From these results CMNX is considered to be a useful drug for the treatment of various infections in the field of obstetrics and gynecology.