Sixteen of 149 patients complaining of impotence of a non-neurogenic or endocrine aetiology and with a penile brachial index of greater than 0.7 failed to achieve an erection following intracavernosal injection of 30 mg papaverine and 1 mg phentolamine. All 16 were shown to have a significant venous leak using digital subtraction cavernosography. Nine of the 13 so far operated upon have had a full return of potency. Repeat cavernosography in three failures showed persistent leakage into crural veins in two and non-ligated superficial veins in one. Impotent men with a normal penile brachial index who fail to respond to papaverine and phentolamine have a venous leak, a curable cause of impotence. Surgical access should allow ligation of all identified leaking veins.