Goldblatt and his co-workers1have recently shown that a sustained increase in blood pressure may be produced in dogs by partial occlusion of the renal arteries. This observation has been confirmed by numerous investigators, including Page,2Prinzmetal and Friedman3and ourselves. Since the hypertension is not relieved by denervation of the kidney, can be produced in animals subjected to previous renal denervation2and occurs even when the kidney has been transplanted into the neck,4the rise in blood pressure appears to be of "chemical" rather than "nervous" origin. Hartwich5showed that ureteral ligation caused a rise in blood pressure in dogs. Similar results were reported by others,6who found that previous denervation of the kidney did not prevent the effect. It has recently been observed7that ureteral ligation may cause a well marked diminution of the blood flow through the kidneys of unanesthetized dogs. Since ischemia of the