Introduction: Urinary tract endometriosis is rare and occurs in about 1% of all endometriotic lesions. About 30% of patients suffer from reduced kidney function at the time of diagnosis. Case Report: A 49-year-old woman presented with a history of abdominal hysterectomy without adnexae because of uterus myomatosus without any signs of endometriosis 6 years before. Now she complained of dysuria and intermittent left loin pain. Sonography and retrograde pyelography demonstrated incomplete ureteric obstruction and scintigraphy revealed a partial loss of kidney function. Intraoperatively frozen section histology and final histologic examination demonstrated a tumorlike intrinsic form of ureteral endometriosis engulfing the left ureter. The patient was treated with uretero-ureterostomy and danazole for preventing recurrence. She is well 28 months postoperatively. Conclusions: In the extrinsic form (about 75% of all cases), ureteral endometriosis is localised to the adventitia or surrounding connective tissue of the ureter, whereas the intrinsic form of ureteral endometriosis is very rare and more often needs aggressive surgery.