Analgesics and topical agents ineffectively inhibit painful erections after penile and urethral surgery. Oral ketoconazole reversibly inhibits testosterone production and has been used empirically at our institution to decrease postoperative erections. We performed a retrospective review of 38 patients who had undergone penile and urethral reconstructive surgery. In all, 31 patients received 400 mg of ketoconazole three times daily for 10-14 days postoperatively (the study group) and seven patients did not receive ketoconazole (the control group). The incidence of postoperative erections, pain, side effects, surgical outcomes and patient satisfaction in each group were compared. Of the control group, 71% reported erections in the immediate postoperative period, and all these patients reported the erections were painful. Only 23% of the patient taking ketoconazole reported postoperative erections, and only 16% reported the erections were painful. We conclude that ketoconazole effectively prevents painful postoperative erections with minimal side effects.