Mean arterial pressure (MAP) is a critical hemodynamic factor. The absence of proper regulation of MAP can have important pathophysiological consequences. Low MAP can cause inadequate blood flow to organs, syncope, and shock. On the other hand, elevated MAP contributes to increased oxygen demand by the heart, ventricular remodeling, vascular injury, end organ damage, and stroke. The arterial baroreflex system is a key controller of MAP and is a complex system. It can be considered in its entirety as an integrative physiological system or in terms of its regulated component parts. Those component parts include MAP, mechanosensory transduction, afferent pathways, central neural circuits, efferent pathways, receptor pharmacology, integration with other key homeostatic inputs, molecular biology, and/or other elements. This chapter provides an overview of each of these individual components but stresses the importance of the integrative nature of this reflex. In addition, this chapter explores common measurement techniques for the baroreflex and explores the baroreflex in diseases.