This review, based on prospective epidemiological studies, indicates the existence of a dose-response relationship between physical activity and coronary heart disease (CHD), which is linear at least up to a certain level of activity. Leisure time physical activity is associated with about a 30-50% reduction in risk of CHD. The benefit of leisure-time physical activity is seen in both men and women, in middle-aged and older subjects and in men with established CHD. Several mechanisms, which could contribute to the protective effect of physical activity on CHD have been identified. Prospective studies suggest that physical activity is also associated with reduced risk of stroke. Overall, the evidence points to the benefit of continued regular moderate physical activity which does not need to be vigorous or sporting, and includes activities such as walking or gardening, readily attainable by large sections of the population. Current evidence supports the recommended guidelines of 30 minutes of moderate physical activity on most days of the week in both primary and secondary prevention of CHD.