We used cost-effectiveness analysis to estimate the health and economic implications of exercise in preventing coronary heart disease (CHD). We assumed that nonexercisers have a relative risk of 2.0 for a CHD event. Two hypothetical cohorts (one with exercise and the other without exercise) of 1,000 35-year-old men were followed for 30 years to observe differences in the number of CHD events, life expectancy, and quality-adjusted life expectancy. We used jogging as an example to calculate cost, injury rates, adherence, and the value of time spent. Both direct and indirect costs associated with exercise, injury, and treating CHD were considered. We estimate that exercising regularly results in 78.1 fewer CHD events and 1,138.3 Quality Adjusted Life Years (QALYs) gained over the 30-year study period. Under our base case assumptions, which include indirect costs such as time spent in exercise, exercise does not produce economic savings. However, the cost per QALY gained of $11,313 is favorable when compared with other preventive or therapeutic interventions for CHD. The value of time spent is a crucial factor, influencing whether exercise is a cost-saving activity. In an alternative model, where all members of the cohort exercise for one year, and then only those who like it or are neutral continue, exercise produces net economic savings as well as reducing morbidity.