The diagnosis of ureteral obstruction caused by endometriosis can be difficult. We present a 51-year-old multiparous Japanese women who had undergone right salpingo-oophorectomy at the age of 19 years. She underwent total hysterectomy, left salpingo-oophorectomy, and adhesiotomy of the right ureter after the diagnosis of myoma uteri and endometriosis was made. Microscopic examination of the surrounding resected tissue confirmed the typical endometriotic origin. In addition to intravenous and retrograde pyelography, computerized tomography was useful to establish the diagnosis of ureteral obstruction caused by an extrinsic mass of endometriotic tissue.