Using a prospective, randomized, controlled design, we examined the effects of behavioral family-based treatment on percent overweight and growth over 10 years in obese 6- to 12-year-old children. Obese children and their parents were randomized to three groups that were provided similar diet, exercise, and behavior management training but differed in the reinforcement for weight loss and behavior change. The child and parent group reinforced parent and child behavior change and weight loss, the child group reinforced child behavior change and weight loss, and the nonspecific control group reinforced families for attendance. Children in the child and parent group showed significantly greater decreases in percent overweight after 5 and 10 years (-11.2% and -7.5%, respectively) than children in the nonspecific control group ( + 7.9% and + 14.3%, respectively). Children in the child group showed increases in percent overweight after 5 and 10 years ( + 2.7% and +4.5%, respectively) that were midway between those for the child and parent and nonspecific groups and not significantly different from either. At 10 years, child height was related strongly to the height of the parent of the same sex (r=.78): children were 1.8 cm taller than their parents, with no differences in height between groups.