Background -Lifetime risk for atherosclerotic cardiovascular disease(CVD) has not previously been estimated, and the effect of risk factor burden on lifetime risk is unknown. Methods and Results -We included all Framingham Heart Study participants who were free of CVD(myocardial infarction, coronary insufficiency, angina, stroke, claudication) at 50 years of age. Lifetime risks to 95 years of age were estimated for men and women, with death free of CVD as a competing event. We followed up 3564 men and 4362 women for 111 777 person-years; 1757 had CVD events and 1641 died free of CVD. At 50 years of age, lifetime risks were 51.7%(95%CI, 49.3 to 54.2) for men and 39.2%(95%CI, 37.0 to 41.4) for women, with median survivals of 30 and 36 years, respectively. With more adverse levels of single risk factors, lifetime risks increased and median survivals decreased. Compared with participants with ≥2 major risk factors, those with optimal levels had substantially lower lifetime risks(5.2%versus 68.9%in men, 8.2%versus 50.2%in women) and markedly longer median survivals( >39 versus 28 years in men, >39 versus 31 years in women). Conclusions -The absence of established risk factors at 50 years of age is associated with very low lifetime risk for CVD and markedly longer survival. These results should promote efforts aimed at preventing development of risk factors in young individuals. Given the high lifetime risks and lower survival in those with intermediate or high risk factor burden at 50 years of age, these data may be useful in communicating risks and supporting intensive preventive therapy. Background -Lifetime risk for atherosclerotic cardiovascular disease (CVD) has not previously been estimated, and the effect of risk factor burden on lifetime risk is unknown. Methods and Results -We included all Framingham Heart Study participants who were free of CVD (myocardial infarction, coronary insufficiency, angina, stroke, claudication) at 50 years of age. Lifetime risks to 95 years of age were estimated for men and women, with death free of CVD as a competing event. At 50 years of age, lifetime risks were 51.7% (95% CI, 49.3 to 54.2) for men and 39.2% (95% CI, 37.0 to 41.4) for Compared with median survivals of 30 and 36 years, respectively. With more with levels of single survivals decreased, than with median survivals of 30 and 36 years, respectively. 5.2% vers us 68.9% in men, 8.2% versus 50.2% in women) and markedly longer median median survivals (> 39 versus 28 years in men,> 39 versus 31 years in women). Conclusions-The absence of established risk factors at 50 years of age These results should promote efforts aimed at preventing development of risk factors in young individuals. Given the high lifetime risks and lower survival in those with intermediate or high risk factor burden at 50 years of age, these data may be useful in communicating risks and supporting intensive preventive therapy.