Analysis of 34 years of follow-up of Framingham Study data provides clinically relevant insights into the prevalence, incidence, secular trends, prognosis, and modifiable risk factors for the occurrence of heart failure in a general population sample. Heart failure was found to be highly prevalent, affecting about 1% of persons in their 50s and rising progressively with age to afflict 10% of persons in their 80s. The annual incidence also increased with age, from about 0.2% in persons 45 to 54 years, to 4.0% in men 85 to 94 years, with the incidence approximately doubling with each decade of age. Women lagged slightly behind men in incidence at all ages. Male predominance was because of a higher rate of coronary heart disease, which confers a fourfold increased risk of heart failure. Heart failure, once manifest, was highly lethal, with 37% of men and 33% of women dying within 2 years of diagnosis. The 6-year mortality rate was 82% for men and 67% for women, which corresponded to a death rate fourfold to eightfold greater than that of the general population of the same age. Sudden death was a common mode of exitus and accounted for 28% of the cardiovascular deaths in men and 14% in women with heart failure. Hypertension and coronary disease were the predominant causes for heart failure and accounted for more than 80% of all clinical events. Factors reflecting deteriorating cardiac function were associated with a substantial increase in risk of overt heart failure. These include low vital capacity, sinus tachycardia, and ECG evidence of left ventricular hypertrophy.(ABSTRACT TRUNCATED AT 250 WORDS)