The pharmacokinetics of imipenem and cilastatin were studied in a group of six healthy elderly male volunteers following the combined intravenous administration of 500 mg imipenem and 500 mg cilastatin sodium as either single or multiple (6 hourly for 6 days) 20 min constant-rate infusions. The pharmacokinetics of both imipenem and cilastatin in the elderly were similar to those of young individuals with mild renal failure (Verpooten et al., 1984). There was no change in the pharmacokinetics of either species with time following multiple-dosing. Correlations existed between total clearance and the glomerular filtration-rate (51Cr-EDTA) for both imipenem and cilastatin.