OBJECTIVES To evaluate the effect of exercise to osteoporosis by bone mineral density (BMD) measurement of athelets comparing normal individuals in general population. METHODS BMD of radium, lumber spine, and femoral neck were measured by single photon absorptiometry (SPA), quantitative CT (QCT), and dual X-ray absorptiometry (DXA) respectively in athletes (n = 162, male 79, female 83) and age matched non-athletes normal population (n = 204, male 91, female 113) in Beijing. RESULTS BMD of all sites in all age groups of both male and female athletes are significantly higher comparing with that in non-athletic population. This predominance in athletes is even more distinctive in peak bone mass. Peak bone mass of male athletes is significantly higher than that of female athletes. Bone loss with age is less apparent in athletes than in control. However, there is an accelerated decline of BMD in lumber spine and femoral neck in 30-39 year age group in both male and female athletes, which may be due to the wanting of physical exercise. CONCLUSIONS Long term regular proper exercise started in adolescence may play a very important role in the prevention of osteoporosis by improving peak bone mass and decreasing bone loss.