This article summarizes recent evidence on the role of physical activity in the prevention of overt and subclinical vascular disease. Epidemiologic data suggest that as little as 30 minutes per day of moderate-intensity physical activity, including brisk walking, reduces the incidence of clinical cardiovascular events in men and women. Regular exercise may also retard the progression of asymptomatic coronary and peripheral arteriosclerosis. Cardioprotective mechanisms of physical activity include reducing adiposity, blood pressure, diabetes incidence, dyslipidemia, and inflammation, and enhancing insulin sensitivity, glycemic control, fibrinolysis, and endothelial function. In a sedentary society such as the United States, public health initiatives that promote moderate increases in activity represent the optimal balance between efficacy and feasibility to achieve desired improvements in cardiovascular health.