Primitive neuroectodermal tumors (PNETs) are rare and aggressive malignant small round cell sarcomas. Primitive urogenital location of PNETs is rare and occurs most frequently in the kidney. PNETs of the upper-urinary tract are exceptional (only one case reported in the literature). Its diagnosis is almost postoperative within pathological study of the operatory specimen, supported by immunohistochemistry and cytogenetics. Treatment is similar in all to that of Ewing's sarcoma and involves surgery, chemotherapy and radiotherapy. We report a new case of upper-urinary tract PNET and discuss the diagnostic and therapeutic problems posed by this particular tumor.