In a randomized, double-blind clinical trial conducted at 13 medical centers, meropenem (1,000 mg given iv every 8 hours) was compared with the combination of clindamycin (900 mg every 8 hours) plus tobramycin (5 mg/[kg · d] in three divided doses) given iv for the treatment of intra-abdominal infections that required surgery and parenteral antibiotic therapy. At the end of treatment, efficacy data on patients who met study inclusion criteria (intent-to-treat) were available for 132 of 215 patients in the meropenem group and 134 of 212 patients in the clindamycin/tobramycin group; 120 (91%) of 132 intent-to-treat patients in the meropenem group were cured, 115 (86%) of 134 intent-to-treat patients in the clindamycin/tobramycin group were cured (P value, not significant). Of the patients treated with meropenem and considered evaluable according to the study protocol, 89 (92%) of 97 were cured, and 81 (86%) of 94 patients treated with clindamycin/tobramycin and considered evaluable were cured. Bacteriologic response rates for all evaluable patients (n = 191) were 96% (93 of 97 patients) among those randomized to the meropenem arm and 93% (87 of 94) among those randomized to the clindamycin/tobramycin arm. Adverse events occurred with similar frequency in both treatment groups; neither seizures nor deaths related to treatment were reported for any patients in either group. The results of this trial demonstrated that meropenem, together with appropriate surgical intervention, was safe and effective in the treatment of patients who had bacterial intra-abdominal infections, most of which were secondary to complicated appendicitis.