Severe hypertension of at least 7 years' duration, due to coarctation of the right renal artery, was treated by reconstruction of the abnormal artery and restoration of blood flow to the coarcted kidney. Renal biopsies revealed normal microscopic architecture in the right kidney and advanced hypertensive pathology in the opposite kidney. After 8 months' observation of persistent, moderate hypertension, the left kidney was removed with prompt return of blood pressure to normal levels during the subsequent 2½ years.These observations demonstrate the precise correlation of hypertension due to renal artery stenosis in the human with the experimental model in rats.