Epidemiologic data based on general population surveillance examining the prevalence, incidence, and outlook of cardiac failure are sparse. The Framingham Study has followed a cohort representative of the general population biennially for three decades and provides such information. Four hundred eighty-five men and women developed first evidence of overt cardiac failure over 30 years. Between the ages of 35 to 64, the annual incidence of heart failure was 3 per 1000 and increased to 10 per 1000 at ages 65 to 94 years. There was a slight male predominance attributed to their greater propensity to coronary heart disease. Most cardiac failure was associated with long-standing hypertension or the presence of coronary heart disease. Risk of cardiac failure was increased two- to six-fold in persons with coronary heart disease; angina conferred half the risk of myocardial infarction. Silent or unrecognized infarctions predisposed equally as typically symptomatic ones; valvular deformity was a less common cause of cardiac failure. Cardiac failure proved to be an extremely lethal condition with a prognosis little better than cancer. The 6-year mortality rate was 82 per cent for men and 67 per cent for women corresponding to a death rate four- to eight-fold greater than that of persons the same age. Cardiovascular mortality was increased six- to nine-fold, stroke four- to seven-fold in men and women, respectively. Approximately 55 per cent of deaths in men and 73 per cent in women were due to cardiovascular causes, and 43 per cent and 44 per cent, respectively, to coronary disease. Sudden death was a common mode of exitus.(ABSTRACT TRUNCATED AT 250 WORDS)