After evaluating approximately 500 patients to identify the cause of erectile dysfunction. I selected 60 patients to receive a therapeutic injection of the vasoactive drugs papaverine and phentolamine mesylate (Regitine) into the corpora cavernosa. Fifty-two patients (87%) obtained erections that were adequate for sexual intercourse; these patients continued a self-injection program. Older patients with vasculogenic erectile dysfunction responded poorly. Ten patients, seven of whom had responded adequately, subsequently had implantation of a penile prosthesis. Although the self-injection group had few complications, 16 of 30 patients (53%) who had long-term follow-up subsequently discontinued the injections.