The aim of this study was to compare the clinical and bacteriologic efficacy of meropenem with imipenem/cilastatin in the treatment of obstetric and gynecologic infections. This was a controlled, multicenter, randomized study with two parallel groups and a follow-up period of up to 4 weeks. A total of 105 hospital in-patients requiring antibacterial parenteral therapy were enrolled, 52 in the meropenem group and 53 in the imipenem/cilastatin group. Both drugs were administered at 0.5 g every 8 hours, by slow intravenous infusion over 20-30 minutes; for meropenem the administration by intravenous bolus injection (over approximately 5 minutes) was allowed. The mean duration of therapy was 5 days for both treatments. At the end of treatment, all 46 evaluable patients in the meropenem treatment group had a satisfactory clinical response, while in the imipenem/cilastatin group 5/49 patients were clinical failures. The difference between the treatment groups in clinical response was statistically significant (100% vs 89.8%; p=.026). A similar result was seen in the intention-to-treat analysis (98% vs 84.6%; p=0.017). Both treatments were well tolerated, but fewer meropenem patients experienced treatment-related adverse events in comparison with imipenem/cilastatin (11.5% vs 15.1%).