Purpose: Erectile dysfunction (ED) is a common sequel of pelvic fracture urethral disruption (PFUD).Those patients with noctural erections may respond favorably to sildenafil, however, little is known about the response to sildenafil in patients with absent noctural erections.In this prospective study we evaluated the response to the treatment of sildenafil50 mg taken once daily in the patients with absent noctural erections.Materials and Methods: From Jan 2009 to Dec 2011, patients with ED due to PFUD were evaluated prospectively.We recorded nocturnal penile tumescence and rigidity with an erectometer, and if nocturnal erections were absent for 3 nights, patients were administrated sildenafil 100mg at bedtime and tested again at the forth night.Penile duplex ultrasound with intracavernous injection was performed to define the causes.All patients received a daily dose of sildenafil 50mg for 12 weeks.Results: 28 patients with absent noctural erections were included in this study and all reported normal erectile function before PFUD.The noctural erections at the forth night in 13 patients (46.4％) were improved.23 (78％) patients completed the daily sildenafil treatment and followup was available.6 of 13 patients (46.2％) with neurogenic ED and 2 of 10 (20％) with arterial ED who had noctural erections induced by bedtime sildenafil showed response to the daily treatment and reported successful intercourse.Conclusions: Patients with absent noctural erections might respond to sildenafil taken daily, the improvement of nocturnal erections inducing by sildenafil taken at bedtime may predict the response to sildenafil taken daily.