Narrowing of the internal and external carotid arteries by a clamp does not lead to hypertension if the carotid sinus nerves remain intact. Subsequent disruption of the carotid sinus nerves results in hypertension. It is concluded that the cause of the chronic hypertension in dogs with constriction of the carotid sinus is not due to altered cerebral hemodynamics, but rather to disruption of the carotid sinus nerves.