Technical Abstract: Childhood obesity is a public health problem. To understand tracking of body weight from childhood to young adulthood, a longitudinal sample of 841 young adults, ages 19-35 years (68% Euro-Americans (EA) , 32% African-Americans (AA)) was studied. These subjects had also participated in any one of five cross-sectional surveys at age 10 years. Body mass index (BMI) was used to determine the overweight status according to the CDC standard of BMI >= 85th percentile. Change in BMI status from childhood (baseline) to young adulthood (follow-up) was used to group the participants into adiposity categories. The baseline mean BMI and baseline adiposity status were positively correlated to the follow-up mean BMI (r = .66) and follow-up adiposity status (r =.39), p <.000l. From baseline to follow-up, the percent of overweight participants increased from 25% to 58%. This increase was due to an alarming shift of 35% of the normal weight participants at baseline into the overweight category in young adulthood (p <.0001). However, only 2.3% of the overweight participants became normal weight in young adulthood (p <.0001). From childhood to young adulthood, the tracking in mean BMI quartile status was 27% (kappa = . 27) among the EA males; 23% (kappa =. 23) among the EA females; 27% (kappa =. 27) among AA males; and 35% (kappa =. 35) among AA females, respectively (p <.001). Also, 20-40% of the participants moved into a higher quartile in young adulthood. These results demonstrate important changes of adiposity status from childhood to young adulthood.