Techniques have been developed to study the role of arterial and vagally innervated cardiopulmonary mechanoreceptors in conscious dogs during rest, exercise, and anxiety or emotional stress. These techniques involve, among others, bilateral reversible vascular isolation of the carotid sinuses and acute reversible interruption of the aortic baroreflex. The carotid sinus, the aortic arch, and the cardiopulmonary receptors tonically inhibit the vasomotor center in the resting dog. The arterial receptors, but not the cardiopulmonary receptors, minimize the lability in arterial pressure at rest and during exercise. During exercise, the arterial baroreceptors are reset to a higher operating point, limit the increase in arterial blood pressure that develops with increasing severity of exercise, and act to return the pressure quickly to the resting level when exercise ceases. The effects on arterial blood pressure are due to reflex changes in total systemic vascular resistance; cardiac output and heart rate are controlled independently of the arterial and cardiopulmonary mechanoreflexes. The cardiopulmonary reflexes have no evident role in the control of arterial pressure during exercise but, in the chronic absence of the arterial baroreflexes, act to decrease the total systemic vascular resistance when exercise ceases.