The incidence and type of congenital anomalies associated with childhood testicular germ cell tumors were studied retrospectively in 25 patients (20 cases of yolk sac tumor and 5 cases of teratoma). Congenital anomalies were observed in 3 patients with yolk sac tumors and in 1 patient who had a mature teratoma. The abnormalities observed included individual cases of retrocaval ureter, diverticulum of the bladder, Down's syndrome and an ipsilateral inguinal hernia. Children with a testicular tumor should be examined closely for congenital abnormalities.