Satisfactory erection with penetration can be obtained in impotent men by the oral or buccal administration of the alpha-adrenergic antagonist, phentolamine. This agent is also used in conjunction with papaverine HCl for intracavernous injection. The previous observation by Gwinup, that 50 mg of phentolamine HCl po, 1.5 hours before coitus resulted in erection in 11/16 patients, is confirmed. This study, using phenoxybenzamine as the placebo, was repeated with success in 36/85 (42.3%) patients. Because of cost and to decrease the waiting time, a buccal form of phentolamine mesylate was administered (20 mg) with erection and penetration in 21/69 (31.8%). There was no correlation between the degree of penile vascular insufficiency or age and the effectiveness of phentolamine. Buccal phentolamine is shown to increase flow velocity in the dorsal penile artery. Phentolamine produces minimal side effects, including hypertension in the subjects.