Numerous studies consistently have shown that higher levels of physical activity are associated with decreased risks of coronary heart disease, cerebrovascular disease, hypertension, non-insulin-dependent diabetes mellitus, colon and, possibly, breast cancer, as well as osteoporosis. The biological processes proposed to explain these inverse associations are highly plausible. If physical activity does reduce the risk of developing these chronic diseases, we also would expect physical activity to delay mortality and enhance longevity. In this article, we review the major epidemiological studies worldwide that have examined the association between physical activity or physical fitness and all-cause mortality. The data from these studies indicate that physical activity is effective in postponing mortality and enhancing longevity. Public health professionals worldwide should emphasize the need to increase activity levels during leisure time, as well as the need to incorporate physical activity into the daily activities of life.