To elucidate the role of arterial baroreceptors in the acute regulation of arterial pressure in the conscious animal, arterial pressure was lowered and raised in intact, conscious dogs, and in dogs after bilateral section of both carotid sinus and aortic nerves (total arterial baroreceptor denervation, TABD). Pressure was altered by intravenous bolus injections and continuous infusions of nitroglycerin and methoxamine and also by hemorrhage. TABD resulted in a change in peak mean arterial pressure 2-4 times as great as that seen in intact dogs following injection of nitroglycerin or methoxamine. However, when the time taken for the arterial pressure disturbance to return to control levels, as well as the absolute change in arterial pressure, was considered (the pressure-time product), responses of dogs with TABD were far greater for nitroglycerin (7-9 times that seen in intact dogs) and methoxamine (11-15 times). Arterial pressure responses of dogs with selective section of the carotid sinus nerves were intermediate but closer to those of intact dogs than to dogs with TABD. With infusion of drugs or following hemorrhage, responses of mean arterial pressure were 3- to 5-fold greater in dogs with TABD than in intact dogs, indicating that the static open loop gain of the arterial baroreceptor system ranged from 2 to 4.