This prospective study was undertaken in an effort to evaluate the role of systemic antibiotic prophylaxis in elective abdominal delivery. Patients (82) undergoing elective cesarean section who were not in labor and who did not have ruptured membranes were assigned on a randomized, double-blind basis to receive a 3-dose perioperative course of placebo or ampicillin. Postoperatively, patients were evaluated for the development of infection-related complications. Patients in the antibiotic group experienced less febrile morbidity, had lower fever indices and developed fewer operative-site infections than did patients in the control group. No patinent in either group developed a potentially life-threatening infection and all infected patients responded promptly to parenteral antibiotic therapy. Because of the limited morbidity associated with elective cesarean section in this patient population, it is concluded that the theoretical risks of antibiotic prophylaxis outweight the expected benefits.