A case of ectopic ureterocele in a 21-year-old male is reported. His chief complaint was right flank pain. We diagnosed ectopic ureterocele in right complete ureteric duplication with upper pole and right heminephrectomy was performed. Postoperative course was uneventful and ureterocele was markedly collapsed. The 10 reported cases with adult male ectopic ureteroceles including our case in Japan are reviewed and some characteristics of this entity are discussed.