Vardenafil, a novel selective phosphodiesterase type 5 inhibitor, was evaluated in its first large-scale at-home trial. A total of 601 men with mild to severe erectile dysfunction (ED) were enrolled in this multi-centre, randomized, double-blind, placebo-controlled trial of 12 weeks of treatment with either placebo or 5, 10 and 20 mg of vardenafil. Primary endpoints were Q3 (vaginal penetration) and Q4 (maintenance of erection) of the International Index of Erectile Function (IIEF). In the intent-to-treat population (n= 580), the changes from baseline for 5, 10 and 20 mg vardenafil (1.2, 1.3 and 1.5, respectively) were all improved (P< 0.001) over placebo (0.2) for Q3 and were similarly improved for Q4 (1.4, 1.5 and 1.7) compared to placebo (0.5)(P< 0.001). All vardenafil doses improved all IIEF domains compared to placebo (P< 0.001). The percentage of successful intercourses was between 71 and 75% for the three vardenafil doses. For the 20 mg dose, 80% of the patients experienced improved erections (GAQ) compared to 30% for placebo. Most frequent treatment-emergent adverse events were headache (7–15%), flushing (10–11%) and up to 7% for dyspepsia or rhinitis. Vardenafil treatment resulted in a high efficacy and low adverse-event profile in a population with mixed ED etiologies.