Background: Childhood obesity is a major risk factor for adult obesity, and obese children tend to be taller than their normal-weight peers. Purpose: The aim of this study is to evaluate whether childhood height influences the probability that normal or overweight children become overweight young adults. Methods: The study involved a multicenter prospective cohort of subjects assessed in both third grade and 12th grade, n=2802. Main exposures were CDC childhood BMI categories and height quartiles from third-grade measurements. Main outcome measure was CDC adult BMI categories from 12th-grade measurements. Associations between childhood height quartiles, childhood BMI categories, and adult BMI categories were assessed using chi-square tests and logistic regression models. Results: Overall, 79% of overweight children remained overweight as young adults. Among children who were overweight or obese, the probability of becoming an overweight or obese young adult was 85% for children in the top quartile of height and 67% for children in the bottom quartile of height (p=0.007). Among children who were normal weight, the probability of becoming an overweight or obese young adult was 25% for children in the top height quartile versus 17% for children in the bottom height quartile (p=0.003). Conclusions: When clinicians classify children by BMI categories and counsel about the risk for future obesity, they should recognize that greater height may be a marker for increased risk of adult overweight and obesity.