Four males with ectopic ureteral opening are reported herein. Case 1 was a 17 year old who complained of miction pain and macroscopic hematuria. Cystoscopy and radiological examinations showed left ectopic ureteral opening into the seminal vesicle associated with left renal agenesis. The left ureter and seminal vesicle were extirpated. Case 2 was a 21 year old who complained of lower abdominal pain. On physical examination, a child's head sized mass was palpable in the midline of the lower abdomen. Operation was performed under diagnosis of intrapelvic tumor, but the mass was cystic dilatation of left ureter which opened into the seminal vesicle. Case 3 was a 19 year old who complained of right CVA colic pain. On cystoscopy, the right ureteral orifice was absent. During the operation, right ureter was found to open into the posterior urethra. Case 4 was a 57 year old who complained of fever. Plain X-ray on the pelvic cavity showed a 82 X 10 mm calcified shadow. CT revealed a right ectopic ureteral opening into the posterior urethra with a ureteral stone in it. On cystoscopy, the right ureteral orifice was identified and pus discharge was observed to flow out of it. Operative exploration demonstrated that the right ureter was inverted Y duplication; one opened into the posterior urethra and the other into the trigone. Seventy nine males with ectopic ureteral opening and 3 with inverted Y ureteral duplication from the Japanese literature are reviewed briefly.