Longitudinal study of 16,936 Harvard alumni, followed for life-style experiences as related to cardiovascular disease (CVD) and longevity, identified 572 first coronary heart disease (CHD) attacks, 1962-1972, and 1,413 all-cause deaths, 1962-1978. Men expending 8.4+ MJ (2,000+ kcal) per week in walking, stair-climbing, and sports play were at 39% lower risk of developing CHD than less active classmates. Attributable risk estimates suggested: there might have been 16% fewer CVD deaths in the alumni population if every man had exercised 8.4+ MJ per week; 25% fewer from total cigarette abstinence; 9% fewer from abolition of hypertension; 6% fewer with less obesity; and 11% fewer CVD deaths in the absence of parental CHD. Discounting the influence of blood pressure status, cigarette habit, net weight gain since college, and parental history of early death, the more active alumni (39% of the population) are estimated to have lived on average one and one-quarter years longer than less active men.