Seventy-six parturients with a clinical diagnosis of early postpartum endometritis were randomized to be treated with either standard therapy--ampicillin, gentamicin and clindamycin--or a new regimen, ampicillin/sulbactam. We deliberately chose to administer 1.5 g of ampicillin/sulbactam rather than a 3-g dose every six hours in order to accentuate any differences that might occur between the regimens. Failure rates, days of therapy and cost of treatment were compared. There was no statistically significant difference (P > .9) in the failure or recovery rates: 4 of 42 (9.5%) patients failed standard therapy vs. 6 of 34 (17.6%) patients in the ampicillin/sulbactam group. The times to recovery were 3.6 +/- 1.8 SD and 3.3 +/- 1.3 days, respectively. There was no difference in side effects or drug toxicity between the two groups. The cost of standard therapy was $355.32 for 3.6 days, whereas ampicillin/sulbactam cost $139.49 for 3.3 days. Therapy with ampicillin/sulbactam may be an equally effective and efficient way to treat patients with early postpartum endometritis.