A multicenter, prospective, open-label, randomized trial compared imipenem-cilastatin (I-C) monotherapy with the combination of clindamycin+gentamicin (C+G). Efficacy and tolerability in the treatment of serious pelvic infections were evaluated in 94 female patients with acute salpingitis, pelvic abscess, or postoperative pelvic cellulitis. Duration of therapy averaged 5.4 days for treatment successes and ten days for treatment failures. The overall treatment success rate was 98% (43 of 44 patients) in the I-C group, compared with 92% (46 of 50 patients) in the C+G group (P = NS). Adjunct therapy for two treatment successes in the I-C group included laparoscopy and surgical removal of a pelvic abscess without change in antibiotics. Both I-C and C+G were highly effective and generally well tolerated for the treatment of salpingitis, pelvic abscess, and postoperative pelvic cellulitis.