Although it is well established that stiff blood vessels contribute to systolic hypertension and increased cardiovascular disease with aging, risk factors for vascular stiffness are still being defined. The Health, Aging, and Body Composition study is a longitudinal investigation of the determinants of physical-functional decline in a well-functioning biracial cohort of 3,075 men and women, age 70–79, in Pittsburgh, PA, and Memphis, TN. Aortic pulse-wave velocity (APWV), an index of vascular stiffness, was measured in 2,488 participants. Self-reported physical activity and exercise habits and fitness/walking endurance were also assessed. Moderate or greater physical activity, exercise, and fitness variables were independently associated with less vascular stiffness, even after inclusion of heart rate, visceral fat, and other correlates of APWV. Physical activity’s association with APWV was particularly strong when levels of physical activity were quite low, suggesting that a minimal amount of physical activity might be sufficient to reduce arterial stiffness in older adults.