In the six years from 1975 through 1980, a total of 12 men died during jogging in the state of Rhode Island. The cause of death in 11 was coronary heart disease (CHD). One man died of an acute gastrointestinal hemorrhage. The prevalence of jogging in the Rhode Island population was determined using a random-digit telephone survey. Among men aged 30 through 64 years, 7.4% +/- 2.6% (mean +/- SEE) reported jogging at least twice a week. The incidence of death during jogging for men of this age group was one death per year for every 7,620 joggers, or approximately one death per 396,000 man-hours of jogging. This rate is seven times the estimated death rate from CHD during more sedentary activities in Rhode Island and suggests that exercise contributes to sudden death in susceptible persons. The occurrence of only one death per 7,620 joggers per year demonstrates that the risk of exercise is small and suggests that the routine exercise testing of healthy subjects before exercise training in not justified.