Endometriosis is the presence of benign endometrial glands and stroma outside the uterus. Urinary system involvement by endometriosis is a rare occurrence accounting for only 1.5 % of all endometriosis cases. Case 1. The patient was a 41 years old woman admitted for right flank pain. The physical and gynaecologic examination was unyielding. Intravenous urography (IVU) revealed stenosis in distal part of right ureter, unfortunately associated with hydronephrosis. Case 2. A 26 years old woman who suffered from colic pain in low abdomen and pelvis. The only positive finding was microscopic hematuria. Abdominal sonography showed hydronephrosis of right kidney and proximal part of ureter. Ureterolysis by an open surgical procedure performed for both patients and histologic examination revealed endometriosis of ureter. Endometriosis of ureter is mainly asymptomatic and unfortunately ends in functionless kidney due to prolonged hydronephrosis. Early diagnosis needs high index of suspicion and intended use of paraclinic aids to save patients normal renal function. An individualized therapy plan depending on the patient's age and the extent of the endometriosis should be attempted.