Artery walls respond to hemodynamic influences of blood flow and blood pressure. Flow and pressure are critical during growth and development as well as adult life. Blood vessels adapt and respond with changes in diameter and wall thickness to accommodate changing hemodynamic environments and needs. Pathologic processes such as: aneurysmal wall degeneration, aneurysm formation and intimal hyperplasia, are similarly influenced by hemodynamic conditions. Hemodynamic factors such as wall shear-stress, particle residence time and heart rate can profoundly influence plaque localization. Hemodynamic conditions can be markedly altered by exercise or drug manipulation and may significantly influence clinical manifestation of vascular disease. The hemodynamic factors important in atherosclerotic vascular disease and the rationale for the beneficial effect of exercise will be emphasized.