Since the classic experiments of Goldblatt in 1934,1followed by the first successful removal of a kidney for treatment of hypertension in the human by Butler2in 1937, there has been an increasing awareness that hypertension of renal origin is a surgically correctable disease. After Smith3reported in 1948 that only 25% of patients undergoing nephrectomy throughout the country were relieved of hypertension, it became apparent that better methods of selection were necessary. During the past few years more refined diagnostic studies such as renal arteriography, radioisotope renography, and differential renal function tests have been employed with increasing frequency and with gratifying results. The relative merits of these tests in the ultimate selection of patients for operation, however, have still not been clearly defined. Experience at the University of Michigan during the past 25 years has paralleled that of other centers throughout the world. In 1942, Ratliff