BACKGROUND: Post-partum endometritis, which is more common after cesarean section, occurs when vaginal organisms invade the endometrial cavity during labour and birth. Antibiotic treatment is warranted. OBJECTIVES: The effect of different antibiotic regimens for the treatment of postpartum endometritis on failure of therapy and complications was systematically reviewed. SEARCH STRATEGY: We searched the Cochrane Pregnancy and Childbirth Group's trials register and the Cochrane Controlled Trials Register. Date of last search: June 2001. SELECTION CRITERIA: Randomised trials of different antibiotic regimens for postpartum endometritis, after cesarean section or vaginal birth, where outcomes of treatment failure or complications were reported were selected. DATA COLLECTION AND ANALYSIS: Data were abstracted independently by the reviewers. Comparisons were made between different types of antibiotic regimen, based on type of antibiotic and duration and route of administration. Summary relative risks were calculated. MAIN RESULTS: Forty-seven trials were included. Overall the studies were methodologically poor. In the intent-to-treat analysis, fifteen studies comparing clindamycin and an aminoglycoside with another regimen showed more treatment failures with another regimen (relative risk (RR) 1.32; 95% confidence interval (CI) 1.09-1.60). Failures of those regimens with poor activity against penicillin resistant anaerobic bacteria were more likely (RR 1.53; 95% CI 1.10-2.13). In four studies that compared continued oral antibiotic therapy after intravenous therapy, no differences were found in recurrent endometritis or other outcomes. There was no evidence of difference in incidence of allergic reactions. Cephalosporins were associated with less diarrhea. REVIEWER'S CONCLUSIONS: The combination of gentamicin and clindamycin is appropriate for the treatment of endometritis. Regimens with activity against penicillin resistant anaerobic bacteria are better than those without. There is no evidence that any one regimen is associated with fewer side effects. Once uncomplicated endometritis has clinically improved with intravenous therapy, oral therapy is not needed.