Subjects will include males who are scheduled to undergo cardiac catheterization or peripheral arteriography at UC Davis Medical Center who have erectile dysfunction and poor response to oral phosphodiesterase-5 inhibitors (Viagra, Cialis and Levitra) as determined by their response to a standardized questionnaire. Dissatisfaction will be defined as a score of 21 or less on the ILEF-5 (International Index of Erectile Function questionnaire).