In the course of radionuclide dynamic studies in 187 consecutive patients who had renal transplants, leakage from a ureter was identified in five cases (an incidence of less than 3%). Demonstrated patterns fell into three classes: 1) perirenal collection (n = 2), 2) peribladder activity (n = 2), and 3) downward dissection (n = 1 case). The sensitivity and specificity of the radionuclide study for detecting ureteral escape of urine after renal transplantation is unknown. However, this study suggests that both indices may be high.