In order to compare the clinical and microbiological efficacy and safety of meropenem with imipenem/cilastatin, 249 patients with intra-abdominal infections participated in an open randomised comparative multicentre trial. Seventy-five men and 57 women (mean age 51 years) were enrolled in the meropenem group and 67 men and 50 women (mean age 52 years) in the imipenem/cilastatin group. The patients received either meropenem, 500 mg q 8 h, or imipenem/cilastatin, 500 mg/500 mg q 8 h by intravenous infusion for up to 17 days (mean 5 days). Ninety-seven of 99 patients (98%) receiving meropenem were clinically cured while 86 of 90 patients (96%) in the imipenem/cilastatin group were clinically cured. The microbiological response was satisfactory in 89 of 94 evaluable patients (95%) receiving meropenem and in 78 of 81 evaluable patients (96%) receiving imipenem/cilastatin. There was no significant difference in clinical and microbiological efficacy between the two treatment groups. Adverse reactions were noted in 26 patients receiving meropenem and in 36 patients receiving imipenem/cilastatin. The present study shows that meropenem is effective and well tolerated in the treatment of intra-abdominal infections.