To help describe the association between exercise endurance and cardiovascular risk factor profiles, 2,606 young and middle-aged healthy adults in the Framingham Offspring Study were given submaximal treadmill tests. For both men and women, exercise endurance was inversely related to resting heart rate (p less than 0.001), body mass index (p less than 0.001), systolic blood pressure (p less than 0.001) and blood glucose (p less than 0.01), and positively related to high density lipoprotein (HDL) cholesterol (p less than 0.05). In men, cigarette smoking (p less than 0.05), high levels of total cholesterol (p less than 0.01) and very low density lipoprotein (VLDL) cholesterol (p less than 0.001) were also associated with poor exercise endurance. After adjusting for age, resting heart rate and body mass index, significant independent associations persisted for HDL cholesterol (p less than 0.05) in both sexes and for systolic blood pressure, VLDL cholesterol, blood glucose and cigarette smoking in men (p less than 0.05). Risk factors associated with overt cardiovascular disease in older individuals are also associated with poor exercise endurance in those who are younger and asymptomatic.