The clinical tolerance and pharmacokinetics of FCE 22101 (sodium (5R, 6S)-6-[(1R)-hydroxyethyl]-2-carbamoyloxymethyl-2-penem-3-carboxylate), a new penem antibiotic, have been studied after giving a single i.v. dose of 4 mg.kg-1 to ten healthy male volunteers. The pharmacokinetics was estimated according to a two-compartment open model. The peak plasma concentration (Cmax) was 15.5 (1.08) micrograms.ml-1, mean (SEM). FCE 22101 was rapidly cleared from the systemic circulation [t 1/2 lambda z = 44.2 (4.2) min; CL = 7.21 (0.47) ml.kg-1.min-1]. The mean apparent volume of distribution at steady-state was 246 (16.9) ml.kg-1. The mean residence time relative to the 10 min infusion was 39.4 (1.5) min. Urinary recovery of FCE 22101 showed wide inter-subject variation, ranging from 10.2 to 53.6% of the dose. No subject complained of adverse effects.