The incidence of coronary heart disease risk factors and the effects of 20 weeks of diet and exercise were studied in 36 obese adolescents. Values for the following risk factors were determined: serum triglyceride level, high-density lipoprotein-cholesterol level, total cholesterol level, systolic and diastolic BP, maximum work capacity, obesity, and presence of coronary heart disease in the family history. Of the subjects, 97% had four or more risk factors. Two subjects possessed all eight risk factors. The adolescents were randomly assigned to either a control, diet therapy and behavior change, or exercise, diet therapy, and behavior change group. From pre- to posttreatment, a 14.8% and 41.4% reduction in multiple risk was noted for the latter two groups, respectively. No significant difference between the control group and the diet and behavior change group was found. In contrast, the exercise-diet-behavior change group reduced multiple risk (P less than .01) more than either of the other groups. It was concluded that obese adolescents are at high risk for the development of coronary heart disease and that exercise in addition to moderate dietary restriction can result in the reduction of multiple coronary heart disease risk.