ONE of the most important recognized factors in the pathogenesis of hypertension is the role of the kidney. In spite of tremendous effort the mechanism by which hypertension is produced in renal disease has remained obscure. It is our purpose to report a case in which malignant hypertension was caused by an extrinsic compression of the right renal artery and permanently relieved by removal of the right kidney. We consider this case worth adding to those already reported because the arterial obstruction was demonstrated by aortography before operation and because severe functional impairment of the contralateral kidney, which existed at . . .