In summary, although many American children (80%) are regularly active, rates of inactivity among adolescent girls, non-Hispanic blacks, and Mexican Americans are cause for concern. One quarter of all US children watch 4 or more hours of television each day, as do 43% of non-Hispanic blacks. Hours of television watching is related to both BMI and skinfold thickness. Physicians and other health care professionals should counsel children and their caregivers on the importance of regular physical activity and decreasing sedentary activities. Intervention strategies designed to promote lifetime physical activity represent a major public health challenge and priority.