The effects of adding exercise to diet for weight control in obese children were evaluated by randomizing obese girls to one of two groups: diet and diet plus exercise. During the first 6 weeks of the treatment, children exercised in a supervised three times a week exercise program, in which they walked or ran 3 miles. Significant decreases from baseline weight and in percent overweight were observed for both groups during the year of treatment. Significant decreases in percent overweight were observed at 0 to 2 months and then at 2 to 6 months for the children who were exercising, whereas percent overweight in children in the diet-alone group decreased only from 0 to 2 months. In addition, a significant improvement in fitness was observed only for children in the diet plus exercise group.