For a quantitative appreciation of the role of the arterial baroreceptor reflex in circulatory regulations in man, studies in chronic, conscious animals are indispensable. Even in animals, however, identifying the arterial baroreceptor reflex performance with accuracy is difficult for various reasons. We propose to attack, first, two technical problems which have seriously hampered our chronic dog studies: (1) Electromagnetic flow signal via a perivascular probe is dependent on arterial pressure. We propose to identify the magnitude of the pressure-dependent change in aortic wall resistance and find ways to correct this error in flow signal. (2) The Edis-Shepherd method for cervical aortic nerve transection is difficult and, even if performed successfully, the denervation is incomplete. We propose to train ourselves in this end alternative techniques. We will be better prepared then to return to the following ongoing researches. (3) Analysis, in aortic nerve denervated dogs, of the carotid sinus reflex performance during change in the head level which causes a very natural forcing of the reflex, and (4) a mild, quick hemorrhage which is another convenient method to evaluate the arterial baroreceptor reflex in conscious and anesthetized states. We continue these experiments, with better techniques for flow measurement and aortic nerve elimination. In parallel with the chronic dog studies, we propose to continue (5) two-part analysis of the reflex control of resistive and capacitive properties of individual vascular beds in the systemic and (6) pulmonary vascular bed in acute dog experiments. We will integrate the notions and quantitative information on the baroreceptor reflex control into a computer model of the complete cardiovascular loop in order to test their validity.