It has been suggested that obesity in childhood may lead early menarche and rapid bony maturation. The purpose of this study is to investigate correlation between bone maturation and obese degree in childhood in Korea. Methods : Height, body weight, BMI, percent body fat were taken 138 patients. Ultrasonic scan was taken through calcaneous of the right foot to evaluate bone age. DA(△age) was calculated from the difference of bone age and chronological age, and it was used in correlation with obese degree. Results : 1. The average age of patients was 11.91±2.86 years old in boys, 11.44±2.27 years old in girls. 2. The average BMI was 20.92±4.53kg/m2 in boys, 19.76±4.05kg/m2in girls, and average percent body fat was 25.13±8.23% in boys, 27.66±5.95% in girls. 3. The average OI(osteo index) was 37.88 in boys, 36.64 in girls, and average bone age was 12.00±2.61 years old in boys, 11.81±2.11 years old in girls. 4. There was significant correlation between DA(Δage) and PBF in boys, but no significant correlation with BMI(p<0.05). 5. There was significant correlation between DA(Δage) and PBF, BMI in girls(p<0.01). 6. There was significant correlation between RA and OI(p<0.01). Conclusion : It is suggested that obese degree may have an impact on early bony maturation especially in case of girls.