Sudden coronary death is a major manifestation of clinical coronary artery disease which doubles in incidence with each decade of life after age 45, with women lagging behind men in incidence by 20 years. Some 14% of heart attacks present as sudden death, and 41% of deaths from coronary disease are sudden deaths. Half of all sudden coronary deaths occur in persons without prior overt coronary artery disease. Persons with established coronary disease are at a three- to fourfold increased risk of sudden death, but the proportion of coronary deaths due to sudden death is no higher. This report examines how sudden death evolves over the long term in the general population and in persons with overt coronary artery disease, and attempts to delineate prime candidates and modifiable predisposing factors using the Framingham Heart Study. In asymptomatic persons the risk of sudden death varies over a wide range in relation to risk factors such as systolic blood pressure, serum cholesterol, cigarette smoking, heart rate, electrocardiographic abnormality and relative weight. Multivariate combination of these risk factors identifies 38.6% of sudden deaths in men and 43.8% of sudden deaths in women in the upper quintile of multivariate risk, which are, respectively, 6.0 and 5.8 times greater than the proportion of sudden deaths in the lowest quintile. When overt coronary artery disease is manifest, the major risk factors have less influence on sudden death risk, which becomes determined chiefly by indicators of intrinsic myocardial damage. With cardiac failure there is an eightfold increased risk of sudden death in men, and cardiac failure without concomitant coronary artery disease imposes a 2.7-fold increased risk.(ABSTRACT TRUNCATED AT 250 WORDS)