Congenital malformations of the seminal vesicle are uncommon, and most of them are cystic malformations. 1 If an insult occurs at approximately the 12th gestational week, the embryogenesis of the kidney, ureter, seminal vesicle, and vas deferens can be altered. Cysts of the seminal vesicle may appear with a mass, dysuria, epididymitis, or obstruction of the gastrointestinal and genitourinary tracts. Approximately two thirds of them are associated with ipsilateral renal agenesis, because both the ureteral buds and seminal vesicles originate from the mesonephric (wolffian) duct. 2 They were first described by Zinner in 1914, 3 and nearly 100 cases had been reported as of 2000. 2,4 Most patients with this anomaly are asymptomatic until the third or fourth decade of life. Some cases have nonspecific symptoms such as prostatism, urinary urgency, dysuria, painful ejaculation, and perineal discomfort. 5 Transrectal ultrasonography provides good visualization of the pelvic structures and allows guidance for aspiration of the cysts. We present the imaging features of a seminal vesicle cyst in a patient with dysuria, increased frequency of urination, and painful ejaculation.