In a nonblind, randomised, parallel-group study, initial empirical monotherapy with meropenem 1 g intravenously every 8 h was compared to an identical dosage of imipenem/cilastatin for the treatment of 66 febrile episodes in 61 adult neutropenic patients. 25/31 episodes treated with meropenem and 24/30 imipenem/cilastatin-treated episodes were still receiving unmodified therapy at 72 h (primary endpoint); this difference was not statistically significant. By the end of the treatment courses, 18/31 meropenem-treated episodes had responded clinically (cured or improved) compared with 18/30 episodes treated with imipenem/cilastatin. Another ten episodes initially treated with meropenem and six episodes treated with imipenem/cilastatia were cured after an additional antimicrobial agent had been administered (cured with modification). Satisfactory bacteriological responses (eradication plus presumed eradication) at the end of unmodified therapy was 9/11 in the meropenem group and 14/16 in the comparator group. Both regimes were well tolerated; however, there were more reports of nausea and/or vomiting in the impenem/cilastatin group (7/33 vs. 2/33 in the meropenem group). The carbapenems meropenem and imipenem/cilastatin appear to be suitable agents for empirical monotherapy of febrile episodes in neutropenic patients. Meropenem may be better tolerated than imipenem/cilastatin, allowing optimal dosing in this patient population.