Physical and sedentary activity in children and adolescents has immediate health benefits and can also set a pattern that carries over into adulthood, resulting in long-term health benefits. Activity levels in a free-living biracial sample of children and adolescents, ages 9-15 yr (N = 995), were examined using a 24-h recall instrument, the Self-Administered Physical Activity Checklist. Selected sedentary activities (television watching and video-/computergame playing) were also assessed. Overall, boys were more physically active than girls and engaged in more heavy physical activity, while girls reported a larger percentage of time spent in light and moderate physical activities. Gender and, to a lesser extent, ethnic differences were seen in the types of activities reported. Although most physical activity occurred after school, children who reported no physical education class during school had less physical activity overall. There was a decrease in moderate physical activity with increasing grade levels in school and an increase in sedentary behavior. Black children reported more sedentary activity than white children, and girls reported more than boys. Although this 24-h recall method has limitations, it allows characterization of the activity of groups of children and provides useful data for policy recommendations.