The single dose pharmacokinetics of temocapril, a novel prodrug type angiotensin converting enzyme (ACE) inhibitor with preferential biliary excretion, were evaluated in 6 patients maintained on haemodialysis and in 1 patient on continuous ambulatory peritoneal dialysis (CAPD). In a crossover design, each haemodialysis patient received a single oral dose of temocapril 1mg after breakfast on two occasions, on dialysis and nondialysis days, at an interval of 1 week. The CAPD patient received a single oral dose of temocapril 1mg. Plasma concentrations of temocapril and its active metabolite (diacid) and ACE activity were determined after drug administration. Area under the plasma concentration-time curves (AUC) in haemodialysis patients on the nondialysis day were significantly greater than those in patients with normal renal function who were used as a reference (p < 0.01). Other pharmacokinetic parameters such as maximum plasma drug concentration (Cmax), biological half-life (t½) and time to reach Cmax(tmax) were not significantly different between the 2 groups. 24 hours after administration, the ACE inhibitions in haemodialysis patients were significantly higher than those in patients with normal renal function. There were no other significant differences between the 2 groups. The peak level of diacid (Cmax) in haemodialysis patients on the nondialysis day was significantly greater than that on the dialysis day (p < 0.05). Other pharmacokinetic parameters such as AUC, t½and tmaxwere not significantly different between these 2 days. These parameters in the CAPD patient were similar to those in the haemodialysis patients on dialysis day. The results suggest that the elimination route of temocapril is mainly via the biliary route, but is partially a route permeated through a dialyser membrane or peritoneal membrane. It is suggested that temocapril is preferable to ACE inhibitors with renal elimination in the treatment of patients with hypertension undergoing dialysis.