BACKGROUND Presumptive antimicrobial therapy is an important aspect of the management of intra-abdominal infections. Together with surgery, antimicrobial combinations are still widely used to achieve the required spectrum of activity. The aim of this study was to evaluate the efficacy of parenteral cefepime + metronidazole vs imipenem-cilastatin for the treatment of intra-abdominal infections in adult patients. METHODS Patients with a clinically confirmed diagnosis of intra-abdominal infection were randomized to one of two treatment regimens: cefepime 2 g iv/12 h plus metronidazole 500 mg/8 h or imipenem-cilastatin 500 mg iv/6 h. The primary measure of clinical response was the decline of pre-treatment signs and symptoms of infection. The duration of follow-up was 30 days. Treatment failure was defined as either a lack of improvement or a worsening of pre-treatment signs and symptoms of infection. Surgical management of the infection was determined by the surgeon-in-charge. RESULTS Of the 122 intended-to-treat patients included in the study, 60 patients (33 men) were randomized to cefepime + metronidazole and 61 (27 men) to imipenem-cilastatin. Cefepime + metronidazole treatment was successful in 52 (87%) patients and imipenem-cilastatin in 44 (72%) patients (p = 0.004). Microbiological eradication was established in similar proportions in both groups (cefepime + metronidazole, 43; imipenem-cilastatin, 38). CONCLUSIONS Further studies are warranted to confirm the better results with the cefepime + metronidazole regimen for the treatment of intra-abdominal infections.