Fundamental and clinical studies on gynecological use of cefotetan (CTT), a new cephamycin antibiotic, were performed with following results. Following the intravenous administration of 2.0 g of CTT, T 1/2 beta in serum was 3.1 hours and longer than the previous cephamycin antibiotics. The yields of CTT from serum to various uterine tissues and discharge from retroperitoneum were about 30 approximately 50%. In clinical use, 14 patients with gynecological infections were administrated CTT, and it showed excellent or good efficacy in all patients. No side effects were noted except 1 transient disturbance in liver function.