In a series of dogs the carotid and aortic pressoreceptor nerves were interrupted by vago-tomy and either stripping the carotid sinus area or actual ablation of the sinus. Clamping the carotids and vertebrals simultaneously with resultant cerebral ischemia produces a rise in blood pressure which is as great as that caused by the carotid sinus reflex. Maximum levels of blood pressure were attained when the degree of cerebral ischemia was barely insufficient to cause respiratory center paralysis. The speed of reaction was usually slow, requiring 30 sec. or more to attain max. levels, but occasionally a precipitous rise in blood pressure occurred immediately after occluding the vessels. A possible relation of this response to essential hypertension is postulated.