In order to define osteoporosis on the basis of bone mineral measurements, one must define an acceptable normal range or fracture threshold. It is clear that the normal range cannot be compared between different ethnic groups. We have measured spinal bone mineral density (BMD) by dual photon absorptiometry in 277 women without spinal fracture, aged 30-91 years, and in 53 women with asymptomatic spinal fracture to provide such a database for normal Korean women. Peak bone mass at the 3rd decade was 1.24 g/cm2. BMD from age 40-69 was strongly correlated with age (r = -0.7) and the annual decrease averaged 0.018gm/cm2. The rate of annual loss slowed by 50% in women after 70% years of age. Fracture threshold was evaluated at the 90th percentile for spinal BMD in patients with vertebral fractures. The fracture threshold of the vertebra was 0.94 g/cm2. Approximately 50% of normal women over 50 years of age had values below this threshold. These findings suggest that the way of developing low bone mass in Korean women is to peak high and lose fast.