In the United States, several well-designed studies have demonstrated the efficacy of short-course antibiotic prophylaxis in cesarean sections. The present prospective study was conducted on 150 patients in a Dutch university hospital in a randomized double-blind fashion. Cefoxitin was administered according to a three-dose, 12 h regimen, the first injection given immediately after clamping of the umbilical cord. The rate of infection among the patients was significantly reduced by prophylaxis, judging from febrile morbidity, endometritis, wound infections, urinary tract infections and need for postoperative antibiotic therapy. The prophylactic use of the cefoxitin was especially effective in the secondary cesarean section population. Three risk factors significantly correlated with increased risk of infection: labor, rupture of membranes and pelvic examination. Postoperative cervical cultures showed a significant reduction of bacteria in the cefoxitin group. No shift towards resistant pathogens was demonstrable.