Congestive heart failure (CHF) is an increasing public health problem. Among Framingham Heart Study subjects who were free of CHF at baseline, we determined the lifetime risk for developing overt CHF at selected index ages. We followed 3757 men and 4472 women from 1971 to 1996 for 124 262 person-years; 583 subjects developed CHF and 2002 died without prior CHF. At age 40 years, the lifetime risk for CHF was 21.0% (95% CI 18.7% to 23.2%) for men and 20.3% (95% CI 18.2% to 22.5%) for women. Remaining lifetime risk did not change with advancing index age because of rapidly increasing CHF incidence rates. At age 80 years, the lifetime risk was 20.2% (95% CI 16.1% to 24.2%) for men and 19.3% (95% CI 16.5% to 22.2%) for women. Lifetime risk for CHF doubled for subjects with blood pressure >/=160/100 versus <140/90 mm Hg. In a secondary analysis, we only considered those who developed CHF without an antecedent myocardial infarction; at age 40 years, the lifetime risk for CHF was 11.4% (95% CI 9.6% to 13.2%) for men and 15.4% (95% CI 13.5% to 17.3%) for women. When established clinical criteria are used to define overt CHF, the lifetime risk for CHF is 1 in 5 for both men and women. For CHF occurring in the absence of myocardial infarction, the lifetime risk is 1 in 9 for men and 1 in 6 for women, which highlights the risk of CHF that is largely attributable to hypertension. These results should assist in predicting the population burden of CHF and placing greater emphasis on prevention of CHF through hypertension control and prevention of myocardial infarction.