The transport efficiency of the dog's pelviureteral system was examined during pacemaker blockade induced by pentobarbital. For an analog representation of transport efficiency, changes in balance level between the input and the output were registered and recorded on a polygraph together with perfusion rate, renal pelvic pressure, ureteral electromyogram and bolus volume. Pentobarbital dramatically blocked the pacemaker activity of the renal pelvis, and the ureter simultaneously became aperistaltic. During the period of pacemaker rest, the balance level was maintained at a high level in all dogs studied, indicating that a part of the perfusion fluid was accumulated in the pelviureteral system. Furthermore, the accumulated fluid overflowed through the aperistaltic ureter as a free flow. These results are discussed in relation to the transport efficiency of normal peristaltic transport.