A clinico-morphological study of 150 bladder tumours showed significant dependence of bladder carcinoma prognosis on some morphological indices most important of which were the grade of malignancy, histological type and deepness of growth and spread along the lymphatic and blood vessels. Likewise, nuclear polymorphism and hyperchromasia, mitotic figure number, atypical mitosis have a direct connection with prognosis, but they are an integral part of malignancy grade determination and do not play an independent role. Nucleolar organizer zone may serve as an additional criterium of neoplasm biological activity, in particular, its role is important in differential diagnosis of bladder transitional cell carcinoma I and benign processes or transitional papilloma.