We analyzed the incidence of prolonged erection (PE) in 495 impotent subjects following intracavernous papaverine chlorhydrate injection to evaluate sexual dysfunction. Patient course was individually assessed. The overall the incidence of PE was 5.05%. The etiology of sexual dysfunction was psychogenic in all cases. No evidence of dose- or age-related PE was observed. Fibrosis of the corpus cavernosum, although more prevalent in PEs greater than 6 hours, was also observed in PEs of a shorter duration. This suggests that a probable predisposing factor might previously be present in some patients. None of the different methods utilized to achieve penile detumescence appears to afford any significant advantage.