The urinary recovery and tolerability of FCE 22101, a broad spectrum injectable penem, were investigated in a multicentre single-blind randomized crossover study of 60 healthy male volunteers. Single 1 g doses of FCE 22101 or placebo were given by intravenous bolus at weekly intervals. FCE 22101 was given either after intake of 750 ml water (treatment A) or after 8 h of water restriction (treatment B). Placebo was given under water restriction (treatment C). Urine samples obtained at timed intervals were assayed for FCE 22101 and its metabolites P1 and P2 by HPLC. The 24 h urinary recoveries of the parent drug and its metabolites were similar after treatments A and B. Mean recoveries +/- S.D were 29 +/- 13% (FCE 22101), 31 +/- 12% (P1) and 7 +/- 2% (P2) of the dose. Transient suprapubic pain or dysuria, or both, were reported by two subjects after treatment A and by six subjects after treatment B. Symptoms were associated with low urine volumes at 0-2 h and low urinary recovery of FCE 22101 and metabolite P1.