The paper is devoted to analysis of the potentialities of radionuclide renography as a method for assessment of the effectiveness of radiotherapy of bladder cancer. The results obtained suggested close correlation between change of renal function and the results of irradiation. Normal renal function was observed in 3 patients, improvement--in 16 patients, and deterioration--in 8 patients whereas a complete effect of radiotherapy brought about the following figures: 5, 11 and 3, respectively. A conclusion was made of a high significance of renography parameters in objective assessment of the results of radiotherapy of bladder cancer in conjunction with other therapeutic modalities.