To assess the contribution of family history of coronary heart disease (CHD) and longevity in parents to 5-year incidence of coronary events in middle-aged men. A prospective study in men from Northern Ireland and the French cities and environs of Lille, Strasbourg, and Toulouse. A total of 10 600 men aged 50-59 years were examined between 1991 and 1994 and followed annually by questionnaire for incident cases of coronary disease. A detailed family history was taken and a quantitative family risk score for CHD was calculated for each subject. Five-year follow-up is complete; all coronary events (coronary deaths, myocardial infarction, and angina) documented by clinical records were reviewed by an independent medical committee. At screening, 9758 subjects were free of clinical and historical evidence of CHD; in this group there were 317 coronary events by 5 years of follow-up. Subjects whose parents had both survived until >/=80 years showed a relative odds of 0.49 (95% CI: 0.31-0.77) for risk of a coronary event compared with subjects whose parents had not survived until >/=80 years old with adjustment for age and nine other risk factors including family history. The pattern of results was similar in France and Northern Ireland, although parental survival was longer in France. Likewise, subjects with a strong family history showed a relative odds of 1.93 (95% CI: 1.25-3.00) compared with subjects without such a history, after adjustment for age and the nine risk factors including parental longevity. The pattern of results was similar in France and Northern Ireland. These results indicate that a family history of coronary disease and parental longevity, although related, act independently of one another and of other major cardiovascular risk factors in predicting 5-year risk of subsequent coronary events.