This study used multiple regression models to estimate associations of various family characteristics and time use with the body mass index (BMI) z-scores of 734 boys and 725 girls aged 5-18y from the Panel Study of Income Dynamics Child Development Supplement 2003. The strongest relationship in the data was between the BMI of the head of household and a child's BMI z-score (p < 0.001). Time spent sleeping, performing sedentary behaviors, and participating in physical activities was not associated with a child's BMI z-score. This suggests that a family-oriented approach to prevent and treat childhood and adolescent overweight is required.