Background: Clinical trials indicate that a sizable proportion of adults have multiple borderline coronary risk factors and may benefit from treatment. Objective: To estimate the relative and absolute contributions of borderline and elevated risk factors to the population burden of coronary heart disease(CHD) events. Design: A prospective cohort study and a national cross- sectional survey. Setting: The Framingham Study and the Third National Health and Nutrition Examination Survey(NHANES III). Participants: White non- Hispanic persons in the Framingham Study and in NHANES III who were between 35 to 74 years of age and had no CHD. Measurements: Occurrence of first CHD events according to 5 major CHD risk factors: blood pressure, low- density lipoprotein and high- density lipoprotein cholesterol levels, glucose intolerance, and smoking. Three categories- optimal, borderline, and elevated- were defined for each risk factor per national guidelines. Sex- specific 10- year CHD event rates from the Framingham Study were applied to numbers of at- risk individuals estimated from NHANES III and the 2000 U.S. Census. Results: Twenty- six percent of men and 41% of women had at least 1 borderline risk factor in NHANES III. According to estimates, more than 90% of CHD events will occur in individuals with at least 1 elevated risk factor, and approximately 8% will occur in people with only borderline levels of multiple risk factors. Absolute 10- year CHD risk exceeded 10% in men older than age 45 years who had 1 elevated risk factor and 4 or more borderline risk factors and in those who had at least 2 elevated risk factors. In women, absolute CHD risk exceeded 10% only in those older than age 55 years who had at least 3 elevated risk factors. Limitations: The generalizability of the findings to persons of other ethnic backgrounds is unknown. Conclusions: Borderline CHD risk factors alone account for a small proportion of CHD events. Background: Clinical trials indicate that a sizable proportion of adults have multiple borderline coronary risk factors and may benefit from treatment. Objective: To estimate the relative and absolute contributions of borderline and elevated risk factors to the population burden of coronary heart disease (CHD) events Settings: A prospective cohort study and a national cross sectional survey. Setting: The Framingham Study and the Third National Health and Nutrition Examination Survey (NHANES III). Participants: White non- Hispanic persons in the Framingham Study and in NHANES III who were between 35 to 74 years of age and had no CHD. Measurements: Occurrence of first CHD events according to 5 major CHD risk factors: blood pressure, low-density lipoprotein and high- density lipoprotein cholesterol levels, glucose intolerance, and smoking. Three categories- optimal, borderline, and elevated- were defined for each risk factor per national guidelines. Sex- specific 10- year CHD event rates f rom the Framingham Study were applied to numbers of at-risk individuals estimated from NHANES III and the 2000 US Census. Results: Twenty- six percent of men and 41% of women had at least 1 borderline risk factor in NHANES III. According to estimates , more than 90% of CHD events will occur in individuals with at least 1 elevated risk factor, and about 8% will occur in people with only borderline levels of multiple risk factors. Absolute 10- year CHD risk exceeded 10% in men older than age 45 years who had 1 elevated risk factor and 4 or more borderline risk factors and in those who had at least 2 elevated risk factors. In women, absolute CHD risk exceeded 10% only in those older than age 55 years who had at least 3 Limitations: The generalizability of the findings to persons of other ethnic backgrounds is unknown. Conclusions: Borderline CHD risk factors alone account for a small proportion of CHD events.