The expressivity of carcinoembryogenic antigen CEA and ABO(H) isoantigens is studied in a group of 40 pelvic and ureteral transitional cell carcinomas. CEA was not shown to be a tumor marker since it is not found in all tumors whereas it is demonstrated in a case of cystic pyelitis. Nevertheless, it seems to be associated with certain prognostic morphologic markers, i.e., grading and vascular invasion. The ABO(H) isoantigens do not seem to be correlated with the prognosis; many advanced-stage and grade tumors showed, in fact, positivity for these isoantigens in most neoplastic cells. Association of histological techniques and immunohistochemical studies does not seem as useful in predicting the course of upper urinary tract transitional tumors as in bladder tumors.