This chapter discusses biomechanics of circulation. Circulation is divided into major circulation and minor circulation. Systemic circulation begins from the left ventricle and derives from the aorta. It contains renal, coronary and mesenteric (splanchnic) circulation. The blood flow is autoregulated in many regions. The blood pressure of arterial circulation is eight times higher than that of pulmonary circulation. This is because of two reasons. The total length of arteries in systemic circulation is much bigger than pulmonary circulation. Also the diameter of pulmonary vessels is bigger than that of arterial system. Blood flow autoregulates in many regions. Pulmonary circulation begins from right ventricle and derives from pulmonary artery. Compared to systemic circulation, blood pressure of pulmonary circulation is low because of above mentioned reasons. Autoregulation does not play a major role in this circulation. This chapter covers the anatomic and functional classification, hemodynamics, application of ohm’s law to circulation, types of flow (laminar versus turbulent flow), compliance of the blood vessels, windkessel vessels and effect, and starling’s law.