OBJECTIVE: To review the pharmacology, pharmacokinetics, clinical trial data, and adverse effects of vardenafil in the treatment of erectile dysfunction (ED). DATA SOURCES: Literature searches were performed using the MEDLINE database (referenced citations through December 2002), and the references of all identified articles were scanned for additional publications of interest. Unpublished information provided by the manufacturer and proceedings of professional meetings were also evaluated. STUDY SELECTION AND DATA EXTRACTION: All available studies were utilized to obtain information regarding pharmacology. Only human studies were used to gather pharmacokinetic, drug interaction, efficacy, and safety data. DATA SYNTHESIS: Vardenafil is a potent and selective inhibitor of the phosphodiesterase 5 (PDE5) enzyme that has been shown to improve erectile function in several populations of men with ED. Vardenafil has a rapid onset of action, is hepatically metabolized, and has a half-life of 4–6 hours. Clinical trials in otherwise healthy men with ED, men with ED and diabetes, and men with ED and a history of prostatectomy have demonstrated vardenafil's efficacy. Adverse effects appear to be relatively mild in intensity and dose dependent, with 22–61% of subjects reporting adverse effects. CONCLUSIONS: Vardenafil is a safe and effective oral agent for the treatment of ED. Its greater potency and PDE5 selectivity compared with sildenafil appear to confer a lower risk of vision-related adverse effects, but other clinical consequences of these differences are currently unclear.