|Background: To evaluate the effects of baseline BMI and BMI change on overweight school children by tracking them for over 6years. Methods: A total of 351 Korean school children were followed from ages 7-8years in 1997 to 13-14years in 2003. Children`s height and weight were measured at ages 7-8years, 9-10years, 11-12years, and 13-14years. Parent`s factors (parent`s weight and height, education level, and income) and child`s behaviors (physical activity, TV viewing, and appetite) were assessed, using a questionnaire which were completed by parents in 2001. Regression analyses and logistic regression analyses were used. Results: Out of all the children, 13.4% were overweight (defined by the International Obesity Task Force reference) at both ages 7-8years and 13-14years. Among the overweight children at age 7-8years, 85.5% remained overweight after 6years, while 48.9% of overweight children at 13-14years were initially non-overweight. The kappa for weight status was 0.56 and the correlation coefficient for BMI was 0.76 between both ages. Increase of BMI was positively associated with BMI at the age of 7-8y after adjusting for parent and child`s factors (β=1.22 P<0.001). The risk of becoming overweight after 6years, after controlling child and parent`s factors, was associated with higher BMI at the age of 7-8y (RR 5.4 95% C.I. 3.2~9.2) or greater increase of BMI over 6years (RR, 4.8; 95% C.I. 2.8~8.2). Increased appetite was also an independent predictor of overweight after 6y, regardless of BMI at the age of 7-8y, change in BMI, or child and parent`s factors. Conclusions: A trend of increasing weight and increase of adiposity were confirmed among Korean school children. The child with greater BMI at the age of 7-8y or higher increase of BMI change over 6y would be a target of health education to interrupt those trends.