New equipment to evaluate the urine transport function of the ureteropelvic system has been developed. Simultaneous measurement of urine bolus volume and electrical activity in the ureter is possible by means of this equipment. A urine bolus volume measuring system, which is based on the heat electrical method, is located in the probe tip, and bipolar electrodes for EMG are located in the stem of the Fr. 4 ureteral catheter. Two kinds of experiments were performed. One was an examination of the new probe through a pervioureteric model using an infusion pump and Nelatons' catheters of various diameters. The other was an animal experiment. The changes in ureteral peristalsis and urine bolus volume in response to diuretics were examined in mongrel dogs through application of this equipment. The following results were obtained: There was a logarithmic relation between perfusion flow rate in catheters used as ureteral models and the values of voltage depression measured by the heat electrical method. The urine bolus volume was calculated closely through a formula which had been developed from the model experiments. In animal experiments, the bolus volume increased significantly and a transient increase in peristalsis was noted after the administration of diuretics although there was no significant change in peristaltic velocity. Some pelvioureteric function parameters, i.e. peristaltic frequency, peristaltic velocity, urine bolus volume, volume, bolus length and ureteral width, are feasible calculations. These results indicate that bolusmetry by using this new probe is a valuable method for evaluation of urine transport function in the pelvioureteric system, and suitable for clinical use as well as animal experiments.