Male Wistar rats, 5-6 weeks of age and about 150g of body weight, were trained for 3, 6 or l0weeks according to a treadmill running program: 15 m/min, 1,000 m/day and 6 days/week. Compared with sedentary control rats, the trained rats gave following results:1. Remarkable decrease in body weight, 2. Significantly lower level of serum cholesterol, 3. Relative increase in lipids loaded on a-lipoproteins , and 4. Distinct enhancement of the incorporation of <14>^C-acetate into liver cholesterol when assayed with slices. These manifestations became more and more obvious as the training continued for longer periods, and the differences between the trained and the sedentary rats were statistically significant after 10-week exercise. The present evidence has provided an additional support to our hypothesis that the physical exercise promotes the turnover of cholesterol in tissues.