['We evaluated the response of sildenafil citrate in patients with prostate cancer treated with three-dimensional conformal radiation therapy (3DCRT) whose sexual function (SF) was known prior to therapy initiation.', "From March 1996 to April 1999, 24 men with median age of 68 years (range 51 to 77) had 3DCRT for localized prostate cancer (median prescribed dose to the planning target volume of 70.2 Gy). These men started taking sildenafil for relief of sexual dysfunction at a median time of 1 year after completing 3DCRT. We used the self-administered O'Leary Brief Sexual Function Inventory to evaluate in series SF and overall satisfaction at three time points. These points were (a) before initiation of all therapies (3DCRT or hormonal treatment [HT]) for prostate cancer, (b) before starting sildenafil (50 mg or 100 mg) but after completion of all therapies, and (c) at least 2 months afterward. Rates of SF were based on the number of men responding to a given question. We tested for significance of these two interventions to change SF by applying the Wilcoxon sign rank test.", 'Prior to all treatments, 20 (87%) of 23 men were sexually potent, with 8 (36%) of 22 fully potent (little or no difficulty for penetration at intercourse). After 3DCRT with or without HT and prior to sildenafil use, 13 (65%) of the 20 potent patients remained potent, with only 2 (11%) of 19 being fully potent. The use of sildenafil citrate resulted in 21 (91%) of 23 men being potent, with 7 (30%) being fully potent. In 16 men responding to the satisfaction question, 10 (63%) and 12 (75%) were mixed to very satisfied with their sex life before 3DCRT with or without HT and after sildenafil citrate use, respectively. This response corresponded to potency and satisfaction scores significantly decreasing and subsequently increasing on average by one unit after 3DCRT and sildenafil citrate use, respectively (P <0.05).'] Does sildenafil citrate effectively reverse sexual dysfunction induced by three-dimensional conformal radiation therapy?