Conduction velocity of excitation in various regions of the canine pelviureter was studied through the simultaneous recordings of electromyograms at four sites of the canine pelvicalyceal preparation. The pelviureteral system was maintained in the condition which was similar to in vivo situation by infusion of oxygenated Krebs-Ringer solution into the renal pelvis at the average flow rate of living dogs. The conduction velocity was slowest in the proximal region of the pelvis where the pacemaker was located, i.e., about 5.8 mm/sec on an average. The velocity gradually increased in the distal region of the pelvis and the ureter. It was suggested that the conduction velocity of excitation was significantly different in the proximal area of the pelvis, the distal area of the pelvis and the ureter.