The nuclear organizer region stained with silver colloid technique(AgNOR)was quantitatively studied in 100 cases of transitional cell carcinoma of the urinary bladder.It was found that the average number of AgNOR granules was significantly different between various grades of transitional cell carcinoma of the bladder and was closely correlated with the prognosis of the patient.It is believed that AgNOR counting is a simple,economic and reliable method for the grading and the evaluation of the biological behavior of the transitional cell carcinoma of the urinary bladder.