Taquini, in 1938, modifying Goldblatt's epochal experiment (1), showed in dogs that reestablishment of the circulation in kidneys rendered completely ischemic for a period of 4 to 6 hours, was followed by an elevation of blood pressure upon removal of the clamp occluding the renal pedicle (2). This observation has been confirmed in dogs, cats, guinea pigs, and rats (3) ; but negative results were obtained in rabbits (4).Previous studies have shown that the rise of blood pressure which follows the termination of temporary, complete renal ischemia is not reversed by 933F (piperidomethyl-3-benzodioxane) (5), proving that the substance which causes the rise of pressure is not an epinephrine-like compound. The elevation of blood pressure is greatly reduced or prevented by the preliminary induction of tachyphylaxis to renin (5), an observation which suggests that the substance responsible for the hypertension is renin or a substance having similar properties of tachyphylaxis. This type of hypertension is not prevented by renal denervation, vagotomy combined with destruction of the spinal cord, or splenectomy (6). According to Taquini (2), blood from a vena cava pocket receiving the return flow of completely ischemic kidneys exhibits a vasopressor action in the Loewen-Trendelenberg preparation. On the other hand, neither Friedman and Prinzmetal (7) nor Mason and Rozzell (8) were able to demonstrate pressor properties in the blood taken from the renal vein of dogs exhibiting Goldblatt hypertension. Extracts of completely ischemic kidneys show greater pressor effects than extracts of normal kidneys (4); similarly, extracts of incompletely ischemic kidneys of dogs (Goldblatt hypertension) contain more pressor material than those of normal kidneys (8, 9).It would seem that in both the hypertension due to partial, chronic renal ischemia (Goldblatt) and that following the termination of complete, acute renal ischemia (Taquini), a pressor principle of renal origin is released by the ischemic kidneys into the general circulation. M a n y have con-