The efficacy and the safety of intramuscular imipenem/cilastatin sodium (IPM/CS) were evaluated in 22 patients with obstetric and gynecologic infections. 0.5 g/0.5 g of IPM/CS was suspended in a lidocaine solution and administered in the gluteal muscle twice a day for 3-7 days. Nineteen patients with intrauterine infections were evaluable for the clinical efficacy and 22 for the safety. 1. Clinical efficacies were excellent in 6 patients, good in 11 and poor in 2, and the efficacy rate was 89.5%. Thirteen out of 14 patients who had not responded to treatments with other previously administered antibiotics showed excellent or good responses to IPM/CS. 2. Causative bacteria were eradicated in 5 patients, decreased in 2, unchanged in 3 and replaced in 3, with an eradication rate of 61.5%. 3. Among 22 patients treated with IPM/CS, an eruption and general itching were observed in 1 patient, but no abnormal laboratory test values were observed.