WE HAVE previously shown that the cerebral circulation participates in the generalized increase in vascular resistance that characterizes human hypertension.1 The beneficial effects of surgical procedures on the sympathetic nervous system in the amelioration of the increased vascular resistance include evidence that perhaps the cerebrovascular resistance is also affected. Such evidence consists of relief from the cerebral symptoms of hypertension and the improvement in the hypertensive eyeground changes. In an effort to determine more precisely the effects of the surgical treatment of hypertension on the cerebral circulation, we have measured the cerebral blood flow, cerebrovascular resistance and cerebral oxygen consumption in a series of patients before and after standard operative procedure performed for the relief of hypertension. METHODS The cerebral blood flow of patients with essential hypertension judged suitable for sympathectomy was determined by the nitrous oxide method2 a few days before operation. Mean arterial pressure was obtained