A randomized double-blind study was undertaken to determine which irrigation solution might be best at cesarean section. A saline placebo was compared with ampicillin sodium and one each of three generations of cephalosporins: cephapirin sodium, cefamandole nafate, and moxalactam disodium. A total of 360 cesarean sections were studied, and comparisons made between antibiotic and control groups relative to demographics, possible risk factors, and multiple measures of postoperative morbidity. The total group was further divided into high- and low-risk labor and repeat cesarean groups. Post-cesarean endometritis was diagnosed in the following frequencies for the group as a whole: placebo (24.6%), ampicillin sodium (8.5%), cephapirin sodium (11.4%), cefamandole nafate (4.6%), and moxalactam disodium (16.4%). Cefamandole nafate consistently demonstrated significant decreases in endometritis and other morbidity measures versus placebo both in laboring patients and the group as a whole.