The prevalence of childhood and adolescents obesity at ages 6 to 17 in Seoul were investigated on 1992. The number of children and adolescents comprised of 3310 boys and 3270 girls. Obesity was defined as weight that exceeded the standard weighter for heigher and sex by more than 20%(relative weight>120%) The results were as follows : 1) The overall prevalence rate of childhood and adolescent obesity was 14.45% The prevalence rate of boys was 15.83% and that of girls was 13.06% on 1992. The overall difference of prevalence rate between boys and girls in significant(p<0.001) 2) The highest peak age is 11 years old. There were two peaks in the prevalence rate of obesity one is from 9 to 11 years old. the other is from 15 to 17 years old. 3) The prevalence rate of overweight that exceeded the standard weight by more than 20% to 29% was 8.62% by more than 30% to 49% was 5.58% and by more than 50% was 0.25% Our study suggests than the prevalence rate of obesity among the children and adolescent in Seoul, Korea is gradually increasing which will affect the future adult population. We feel it is needed further investigation to determine the causes of increasing rate of obesity and early establishment of preventive programs.