The immediate and long-term risks associated with overweight in childhood and adolescence are best considered separately. Short-term mortality is rarely associated with overweight of the young. The greatest health burden of overweight in children and adolescents arises from long-term consequences. Long-term follow-up studies of children and adolescents indicate that the risk of adult overweight is about twofold greater for individuals who were overweight as children compared with individuals who were not overweight. Persistence is greatest for extreme overweight and when overweight is carried through late adolescence. The few studies of long-term health consequences in adolescent males find that even moderate overweight is associated with excess mortality in adulthood. Females have been studied infrequently; it appears that overweight confers long-term health risks, but these are less severe. However, because of concern about weight preoccupation in this age group and lack of data of sufficient precision to support specific recommendations, weight guidelines for children and adolescents are not now warranted.