The effects of the autonomic nervous system on ureteral functions were investigated by application of stimulating and blocking drugs. These effects were differentiated from those due to a change of urine flow by perfusing the renal pelvis with isotonic saline. Peristaltic frequency was readily increased by higher flow volume, but was rarely affected by blockage of alpha-adrenergic and cholinergic receptors. The ureteral pacemaker could be activated by alpha-stimulation and inhibited by beta-stimulation. During perfusion of renal pelvis at a pressure of 12 mm Hg, transport capacity of the ureter could be significantly increased either by alpha-blockade or beta-stimulation. Stimulation of alpha-receptors decreased transport capacity, whereas stimulation of cholinergic receptors remained ineffective. These experiments suggest that responses of sympathetic stimulators and blockers are brought about by their influence on ureter muscle tone. The therapeutic value of these drugs is discussed.