The effects of exercise (10000 walk steps/day) and diet (1500 kcal/day) for 4 months on coronary risk factors (obesity, hypertension, serum lipid and lipoprotein abnormalities) were studied in 332 obese, middle-aged subjects. Body weight, skinfold thickness, systolic and diastolic blood pressures, serum lipid and lipoproteins (total cholesterol, triglyceride, and beta-lipoprotein) improved significantly (p less than 0.05) during the program. The degree of improvement in blood pressures, serum lipids and lipoproteins was greater in abnormal blood pressure (greater than 140/90 mmHg) or abnormal serum lipid group than in normal group. A significant correlation was observed between daily number of walk steps and the improvement of body weight, diastolic blood pressure and HDL-cholesterol. Increase of daily steps during the program showed a significant (p less than 0.05) correlation to the change in HDL-cholesterol. It was suggested that mild exercise characterized by brisk walking was effective in the treatment of obesity, hypertension and low HDL-cholesterolemia in obese, middle-aged subjects.