Impotence is a possible consequence of treatment of pituitary adenomas and prostatic carcinomas. Following pituitary irradiation, the effect has been attributed to decreased gonadotrophins, while a variety of mechanisms, primarily vascular and neurogenic, have been proposed to explain the impotence following irradiation of prostatic carcinomas. Men with impotence of any etiology have been entered on a program to evaluate prospectively the efficacy of intracavernosal injection of vasoactive compounds in producing a satisfactory erection with pharmacologic means. Ten of these men had developed impotence following therapy for pituitary adenomas (2) or prostatic carcinomas (8). Test doses of 0.1 to 0.5 ml of a phentolamine (1 mg/ml) and papaverine (30 mg/ml) mixture were used; the dose was titrated to produce an erection deemed sufficient for vaginal penetration. All patients achieved a satisfactory response (i.e., tumescence and rigidity) lasting 10 minutes to 3 hours. Seven patients have continued in the pharmacologic erection program, with six patients functioning normally, and the remaining patient noting decreased tumescence after 18 months of treatment, but adequate erections are maintained with supplemental penile ring. Two patients have discontinued intracavernosal injections due to inconvenience, and one patient was lost to follow-up. Recent substitution of prostaglandin E1 (PGE1) has produced similar results and has replaced the phentolamine-papaverine combination. These preliminary results indicate that pharmacologic erection can be achieved in patients with impotence related to the treatment of pituitary and prostatic neoplasms and represents a reasonable alternative to implanted penile prostheses.