This will be a multi-center, randomized, double-blind, placebo-controlled, parallel-group study in 300 erectile dysfunction patients. Patients will complete a screening visit (V1) to determine eligibility for the study based on the International Index of Erectile Function (IIEF) erectile function (EF) domain scores, patient history and safety measures. Patients that meet the entrance criteria for this study will enter a 4 week, drug-free run-in period to establish a baseline for the erectile function domain score and to meet the criteria for participation in the study.