All body tissues depend on adequate perfusion to ensure delivery of oxygen and nutrients, in addition to the clearance of carbon dioxide and other waste products. Perfusion may be reduced if there is a fall in cardiac output or arterial blood pressure. Hypoperfusion of the vital organs constitutes shock and is a life-threatening emergency. Many disease states and drugs cause a fall in the cardiac output, blood pressure, or both. This chapter outlines the neural, hormonal and intracellular mechanisms involved in the regulation of cardiac output and arterial blood pressure. Furthermore, we discuss how cardiovascular stability may be restored by optimising preload, systemic vascular resistance, myocardial contractility or heart rate.