A longitudinal study design was used to examine factors related to change of body mass index (BMI) over a 1-year period in 307 Chinese children, aged 7 and 8 years, in Taiwan. Standardized instruments were used to measure the children's food intake, physical activity/inactivity, and physical fitness, as well as maternal BMI. Results suggested that a high baseline BMI, poor aerobic capacity, and a high maternal BMI were significantly correlated with increased BMI at 12 months' follow-up. A higher baseline BMI, an overweight mother, increased television viewing and computer time, and poorer aerobic capacity were identified as predictors for weight gain in children (F=207.67; P<.001; adjusted R2=0.752). These findings suggest that health care providers need to include the family in children's health care visits and incorporate an assessment of maternal weight status and children's BMI status, activity levels, and aerobic capacity into patient care and education.