Cardiovascular disease is the primary cause of morbidity and mortality in the western world. Complex hemodynamics play a critical role in the development of atherosclerosis and the processes of aging, as well as many other disease processes. Biofluid mechanics play a major role in the cardiovascular system and it is important to understand the forces and movement of blood cells and whole blood as well as the interaction between blood cells and the vessel wall. Fundamental fluid mechanical, which are important for the understanding of the blood flow in the cardiovascular circulatory system of the human body aspects are presented. Measurement techniques for model studies such as LDA, ultrasound, and MRI studies will be discussed. Viscosity and flow behavior changes specifically the creation of vortices and flow disturbances can be used to show how medication can influence flow behavior. Experiments have shown that hemodynamics may have a strong influence on the creation of aneurysms and varicose veins. Other factors such as vessel wall structure are also important. In preliminary studies, it has been demonstrated that geometry and elasticity of vessel walls help determine flow behavior. High velocity fluctuations indicate flow disturbances that should be avoided. Health care practitioners must understand fluid dynamic factors such as flow rate ratio, pressure and velocity gradients, and flow behavior, velocity distribution, shear stress on the wall and on blood cells. These mechanical factors are largely responsible for the deposit of blood cells and lipids, a leading cause of atherosclerosis. The interaction between blood cells and of the cells with the vessel, leads to the formation of plaques and agglomerations. These deposits are found predominantly at arterial bends and bifurcations where blood flow is disturbed, where a secondary flow is created, and where flow separation regions are found. Experiments on hemodynamic effects in elastic silicon rubber models of the cardiovascular system with flow wire, stents, or patches for vessel surgery will be discussed. These studies can be important in improving diagnostics and therapeutic applications.