A 29 year-old male with the complaints of two steps urination and sense of residual urine was admitted. At cystoscopy, a ureterocele was found between the normal left ureteric orifice and the bladder neck. Excretory urography demonstrated a radiolucent area in the bladder and a left lower hydroureter. Retrograde pyelography revealed that the left ureter was divided into two branches. Operative exploration demonstrated that the left ureter was an inverted Y ureteral duplication with an ectopic ureterocele; one opened into the ureterocele and the other into the trigone. We resected the ureterocele wall. Four months later, a voiding cystogram did not show vesicoureteric reflux. Now, he has no symptoms and the results of examination are normal. An inverted Y ureteral duplication is the rarest of all anomalies of the ureter. A review of the literature revealed 36 cases reported previously. Clinical analysis was obtained by reviewing 26 of these cases and adding our own (male 10: female 17, average age: 23 years). Complication included 6 cases of ectopic ureteral opening, 6 with blind-ending branch and 5 with ureterocele. The symptoms of this disease depended on the complicating anomalies. The present case was the 5th one of an inverted Y ureteral duplication with a ureterocele in the world literature.