Over 30 years of surveillance of 5127 subjects free of CHD, 760 men and 574 women developed overt CHD, and there were 160 sudden deaths in men and 73 in women. Among those who sustained clinically manifest CHD, the sudden death risk was increased 6.7 times that of those without an interim event. Although the relative risk was comparable in the two sexes, CHD did not eliminate the female advantage over men. Myocardial infarction imposed a greater sudden death risk than angina pectoris, and silent infarctions were as dangerous as symptomatic infarctions. Onset of CHD put young and old at equal risk of sudden death. Some 40% of sudden deaths occurred in the 4% of the general population with overt CHD. The proportion of coronary attacks presenting as sudden death increased from 13% at ages 35 to 64 years to 20% at ages 65 to 94 years. The fraction of CHD deaths classified as sudden deaths was lower in those with than without interim CHD. In those with established CHD, factors reflecting ischemic myocardial damage and cardiac failure were the chief predictors of sudden death. The proportion of CHD deaths presenting as sudden deaths has not declined in subjects with prior CHD over three decades, despite a national decline in the overall CHD mortality rate.