Traditional risk factors such as smoking, hypertension and being overweight have received considerable attention in recent years, whereas physical activity as a preventive strategy does not enjoy the same public attention. In recent years the level of physical activity has decreased dramatically in children and adolescents in favor of time spent on the internet and in front of the TV. If this trend is allowed to develop along the same direction, a sharp increase in cardiovascular disease can be anticipated. The protective action of physical activity on the cardiovascular system has been well documented in large numbers of patients, and the basic physiological mechanisms have been elucidated. Metabolic changes comprise loss of weight, reduction in triglyceride and LDL levels, as well as an increase in HDL. Insulin sensitivity is enhanced in all tissues postponing the manifestation of diabetes mellitus. Shear forces created by physical activity induce ecNOS within the endothelial lining of the arteries. This enzyme is responsible for controlling vasomotion through the elaboration of NO which causes vasodilation in the smooth muscle within the vessel wall. Utilization of preformed collateral vessels has been postulated repeatedly; so far, however, it only could be documented in animals, not in humans. Nearly all studies concerned with primary prevention have shown a significant negative correlation between energy expenditure during exercise and cardiovascular mortality, even light and moderate exercise will result in a lower incidence. In order to eliminate a sedentary life style in children and adolescents, adequate programs should be initiated in all schools; they should aim for 60 min of physical activity on a daily basis.