Data from 3125 patients (3220 patient exposures) treated with meropenem were compared with those from 2886 patients (2960 patient exposures) treated with a variety of comparator agents including cephalosporins (alone or in combination with aminoglycosides or an anti-anaerobe agent) and imipenem/cilastatin. Patients treated included those with bacterial infections of the lower respiratory tract, urinary tract and skin and soft tissues, abdominal, obstetric and gynaecological infections, meningitis, febrile episodes in neutropenic patients and paediatric patients with infections. In three studies, meropenem was administered intramuscularly; in the remainder, meropenem was given by 15-30 min iv infusion or by bolus injection over approximately 5 min. The usual dosages were 500 mg or 1 g 8 hourly in adults and 10 or 20 mg/kg 8 hourly in children. In bacterial meningitis, the meropenem dosage in adults was 2 g 8 hourly and 40 mg/kg 8 hourly in children. The overall pattern and frequency of adverse events with meropenem were similar to those of the other beta-lactam antibiotics with which it was compared. The most frequently reported adverse events were diarrhoea, rash, nausea and vomiting, thrombocytosis, eosinophilia and changes in hepatic biochemistry. Abnormal laboratory tests occurred with similar frequencies between meropenem and the comparator agents. The safety profile of meropenem was similar in adults and children, and the presence of renal impairment did not alter the safety profile of meropenem. Experience in clinical studies in 3220 patient exposures has revealed no unusual or unexpected toxicity. The possibility of administration by either iv infusion or bolus injection with a low incidence of nausea and vomiting also provides flexibility in the clinical management of patients. Moreover, the low incidence of reported seizures and good tolerability at high doses, make meropenem particularly useful for the treatment of meningitis and other indications which carry a risk of seizures, or in the treatment of serious infections where high doses of antibiotics are frequently indicated.