Publisher Summary Vasopressin is a cardiovascular peptide that has widespread actions and is essential in maintaining cardiovascular balance by acting at many sites, including the blood vessels, heart, kidney, and central nervous system. The multiplicity of these actions is based on the distribution of the classic vasopressin receptors, namely, Vi, vascular receptor; V2, renal receptor; V3, pituitary receptor; and oxytocin receptor. One of vasopressin's most prominent actions is its potent vasoconstriction of most vascular beds via stimulating the Vi receptors. This vasoconstrictor response to vasopressin is consistent with the distribution of the Vi receptors. In addition to vasoconstrictor activity, vasopressin acts directly to decrease both heart rate and cardiac output. Vasopressin also increases the sensitivity of the baroreflex, thereby leading to an enhanced suppression of heart rate. Vasopressin modulates other major systems that play a role in cardiovascular function, such as potentiating the action of catecholamines and decreasing renin release by the kidney. The other major cardiovascular function of vasopressin is to protect blood volume and osmolality via stimulation of V2 receptors. From a chronic perspective, this leads to increased water retention and enhanced blood volume, thus adding protection against blood volume depletion or volume loss due to dehydration. Moreover, vasopressin agonists and antagonists are rapidly emerging as therapeutic agents for cardiovascular disorders such as vasodilatory shock states, hypertension, and heart failure.