The incidence of myocardial infarction and symptoms of coronary heart disease (CHD) were investigated in a prospective Finnish population study. Drawn from four geographical areas in Finland the study population comprised 5 438 men and 4 924 women aged 30-59 at entry. The results are based on a re-examination of the study population after a mean follow-up time of six years. The average annual incidence of coronary death was 3.8/1 000, and that of non-fatal infarction 6.5/1 000 in men and 0.4/1 000 and 2.1/1 000 in women. Ten per cent of all infarctions were silent, revealed only by ECG changes. Cases of new angina pectoris comprised 40% of all the new events in men but 80% in women. This descriptive report serves as the basis for subsequent analyses comprising risk factors for different CHD manifestations.