Respiratory, heart, and circulatory movements that can be detected without contact by Doppler radar are concentrated not only in the thorax, where the lungs and heart lie, but they also occur in the abdomen, which moves during respiration, and at other points on the body where superficial pulses are present. This chapter first describes the motion associated with breathing and how this motion affects the skin surface motion. It then discusses the location and anatomy of the heart, the electrical and mechanical events that cause contraction, the motion of the heart during contraction, and how that motion affects chest wall motion. The chapter also describes the location and structure of the arteries and veins, how they distend as the blood pressure varies during the cardiac cycle, and how this distension affects the skin surface motion. Doppler radar measurement of heart and respiration is a measurement of surface motion.