Background: Vardenafil is a phosphodiesterase type 5 inhibitor, used in erectile dysfunction. This study aimed to evaluate the pharmacokinetics and tolerability of vardenafil following a single oral administration in healthy male subjects. Methods: A randomized, double-blind, placebo-controlled, single dosing, dose-escalation study was conducted in 30 healthy subjects. A single oral dose of vardenafil or placebo was given to 10 subjects (8 active + 2 placebo) in each dose group of 5, 10 and 20 mg. Serial blood and urine samples were obtained up to 48 hours for pharmacokinetic analysis. Vardenafil and its metabolite were detected by high performance liquid chromatography tandem mass spectrometry assay. Results: A total of 45 adverse events (AE) were reported in 22 subjects, including 5 AEs from placebo treatment, and all the AEs were mild, except one case of moderate nasal stuffiness. Vardenafil was absorbed after a single oral dose, with the $t_{max}$ of 0.5-1.0 hours. The $C_{max}$ and $AUC_{last}$ were $10.21{pm}3.68$ ug/L($mean{pm}SD$) and $18.08{pm}7.44;ug{ imes}h/L$ in 5 mg dose group, $19.79{pm}12.13$ ug/L and $38.61{pm}21.04;ug{ imes}h/L$ in 10 mg dose group and $53.16{pm}37.01$ ug/L and $110.05{pm}69.65;ug{ imes}h/L$ in 20 mg dose group. Dose-linearity on $AUC_{last}$ and $C_{max}$ of vardenafil were observed in three dose groups. In all dose groups, the fraction excreted in urine was less than 1%. Conclusion: The vardenafil was tolerable over a single dose range of 5 - 20 mg. The pharmacokinetics of vardenfil after a single oral dose was explored and linear pharmacokinetic characteristics were observed over the dose range of 5 - 20 mg in healthy subjects.