Impaired blood supply to one kidney as a cause of generalized arterial hypertension has been known for many years.1,2 The classical experiments by Goldblatt3 in 1934 Placed this etiology on a firm foundation. Since then many nephrectomies have been Performed for this reason but with cure of the hypertension in only a disappointing minority because cases of renal parenchymal disease as well as those with renal arterial disease were being so treated. Thompson and Smithwick4 in 1952 found that their best results came when the origin of the renal ischemia was in the renal artery rather than in the kidney proper. Although nephrectomy is an accepted method of therapy, the vasculature of the kidney removed in cases of renal artery stenosis or occlusion is relatively normal on pathological examination because it has been "protected" from the nephrosclerotic changes incident to the hypertension. The remaining kidney is unprotected.