A case of ureteral endometriosis is reported A 42-year-old woman visited our clinic on December 3, 1985, with the complaint of right lumbago. Intravenous pyelography showed right hydronephrosis and retrograde pyelography revealed ureteral stenosis at 11 cm from right ureteral orifice and 2 cm long. Primary right ureter tumor was suspected. The operation was performed on January 16, 1986 and revealed periureteral mass. The mass was removed with ureter and ureteroureterostomy was performed. The pathological diagnosis was extrinsic ureteral endometriosis. Ureteral endometriosis has rarely been described and only 17 cases have been reported previously in Japan.