A 30-year-old man presented with a 7-month history of chronic partial priapism and sexual dysfunction following blunt perineal trauma. Duplex penile ultrasound confirmed high flow priapism and color flow Doppler ultrasound diagnosed an arteriovenous fistula within the left corpus cavernosum. This lesion was corrected via corporeal exploration and ligation of the artery feeding the fistula. The use of color flow Doppler ultrasound to diagnose this unusual condition obviated the need for angiographic studies. This rare condition of posttraumatic priapism may be diagnosed by noninvasive means. The pathophysiology, diagnosis and treatment of posttraumatic priapism and review of the literature are discussed.