The purpose of this study was to investigate the relationship between body fat and risk factors of chronic diseases in obese children and eventually to contribute to the prevention and treatment of childhood obesity. Anthropometric parameters such as height, weight, skinfold thickness, circumferences, body fat content were measured in 55 obese subjects of age 5-20. Blood pressure, serum components, daily food intakes were also considered. The average age of the subjects was 12.5$pm$3.3yrs and the mean obesity index was 64.7$pm$21.3%. The average percentage of body fat was 35.6$pm$5.4% and the mean weight of lean body mass was 45.3$pm$13.9kg. Mean total muscle weight of the subjects was estimated to be 34.11$pm$1.3kg. The mean systolic and diastolic blood pressures of the obese were 134.8$pm$15.8mmHg and 69.6$pm$11.6mgHg respectively. The concentrations fo serum triglyceride, total cholersterol, HDL-cholesterol, LDL-cholesterol were estimated to be 246.0$pm$136.4mg/dl, 257.0$pm$54.3mg/dl, 48.2$pm$13.1mg/dl and 158.9$pm$53.5mg/이 respectively. The concentrations of serum GOT and GPT were 34.6$pm$17.1U/L and 24.7$pm$15.3U/L. The mean content of uric acid is serum was 6.2$pm$1.9mg/dl. Of these 55 children, 82% has hyperlipidemia, 26% was abnormal liver function and 24% was hyperuricemia. One patient was diabetic. Eighty seven% of them have developed more than one complications.