The pharmacokinetics of tinoridine was studied after oral administration (200, 400, and 800 mg in random order) to six healthy subjects and (200 mg) to patients with renal disease. Plasma concentrations of tinoridine were determined by GLC with electron-capture detection and urine concentrations by HPLC. The plasma half-life of tinoridine was about 8.2 h in healthy subjects and was not affected by renal failure. Total body clearance (Clc/F) was very high, but renal clearance was small, about 0.30 1.h-1. There was no correlation between dose (200 mg vs 400 or 800 mg) and Cmax or AUC, suggesting a first-pass effect. Renal failure did not affect pharmacokinetic parameters. However, there was a strong linear correlation between Cmax and age (r = 0.919) and AUC and age (r = 0.838). These results suggest an increase of bioavailability in the elderly.