The relationship between energy intake, physical activity, and body fat was investigated in the baseline visit of 2379 black and white girls aged 9-10 y enrolled in the National Heart, Lung, and Blood Institute Growth and Health Study. Three-day food records, three-day physical activity diaries, physical-activity-patterns questionnaires, and an assessment of the number of hours of television and video watched were obtained. Multivariate-regression analyses showed that age, the number of hours of television and video watched, the percent of energy from saturated fatty acids, and the activity-patterns score best explained the variation in body mass index and sum of three skin-fold-thickness measurements for black girls. The best model for white girls included age, the number of hours of television and video watched, and the percent of energy from total fat. These results indicate that body fatness is related to energy intake and expenditure in both black and white girls. Longitudinal studies will help assess the value of these variables in predicting changes in body fat.