Coronary calcium was found in 22.4% of men and 7.9% of women. A total of 9 acute events occurred in men at a mean age of 46 years, including 7 of 364 men with coronary calcium (1.95%) and 2 of 1,263 men without coronary calcium (0.16%; p < 0.0001 by log-rank). No events occurred in women. In these men, coronary calcium was associated with an 11.8-fold increased risk for incident coronary heart disease (CHD) (p = 0.002) in a Cox model controlling for the Framingham risk score. Among those with coronary artery calcification, the risk of coronary events increased incrementally across tertiles of coronary calcium severity (hazard ratio 4.3 per tertile). A family history of premature CHD was also predictive of incident events. The marginal cost effectiveness, assuming a 30% improvement in survival associated with primary prevention among at-risk men, was modeled to be 37,633 dollars per quality-adjusted life year saved.