Physical inactivity, as manifested by a sedentary lifestyle, is considered to be one of the major risk factors of coronary heart disease (CHD). In this article, the impact of inactivity as a risk factor on CHD and as a cause of cardiovascular and systemic dysfunction is described. Epidemiologic studies indicate that inactivity can be as harmful to the cardiovascular system as cigarette smoking and other risk factors. The effect of inactivity on mortality from CHD and on the functional capacity of the cardiovascular system is presented along with the effects of activity and exercise on the other major risk factors, stressing the negative effects of inactivity.