In an open, randomised, multicentre trial, the efficacy and tolerability of empirical meropenem monotherapy (1 g intravenously every 8 hours) and cefotaxime (2 g every 8 hours) plus metronidazole (0.5 g intravenously every 8 hours) for 5 to 10 days was compared in 94 patients with serious intra-abdominal infection who required surgery. Eighty-three patients had an evaluable clinical response. Significantly more patients in the meropenem group had a satisfactory clinical response at the end of treatment (41/43 [95.3%] vs 30/40 [75.0%]; p = 0.008). The bacteriological response was also higher in the meropenem group (31/33 vs 26/32). In the bacteriologically evaluable population, a satisfactory clinical response was observed in 31/33 of those who received meropenem compared to 24/32 of the cefotaxime/metronidazole recipients (p = 0.03). Empirical meropenem monotherapy should prove a useful alternative to the currently standard combination treatment for serious intraabdominal infections.