The mineral content and width of bone can be determined noninvasively by “bone densitometer”, which measures the absorption by bone of a monoenergetic photon beam that originates in a radioactive source(Iodine-125 at 27.3 Kev). The intensity of the beam transmitted by the bone is measured by a scintillation detector. The bone mineral density is obtained from dividing the bone mineral content by bone width. Since Cameron and Sorenson, in 1963, first described the photon absorptiometry, many investigators have studied this method and applied it clinically. In order to determine the bone density of normal koreans, and compare it with that of fracture risk group, we measured the bone density of the distal one third of the nondominant radius in 152 normal persons(55 male, 97 female), and 54 patients(23 male, 31 female) having the risk of spontaneous fracture from the third to seventh decades. This data were also compared with those of normal Caucasians. The results were as follows. 1. The average bone densities(gm/cm²) of normal men from the third to the seventh decades were 0.773 ±0.055, 0.749 ±0.070, 0.770 ±0.060, 0.797 ±0.053, 0.664 ±0.126, respectively and those of normal women were 0.680 ±0.058, 0.680 ±0.036, 0.674 ±0.052, 0.608 ±0.084, 0.523 ±0.093, respectively. 2. The average bone densitied(gm/cm²) of fracture risk men from the third to seventh decades were 0.647 ±0.072, 0.719 ±0.050, 0.729 ±0.085, 0.699 ±0.064, 0.562 ±0.049, respectively and those of fracture risk women were 0.603 ±0.049, 0.061 ±0.021, 0.326 ±0.034, 0.494 ±0.045, 0.430 ±0.035, respectively. 3. There were statistically significantly differences in the bone densities between the normal population group and the fracture risk group. 4. The average bone densities(gm/cm²) of normal koreans were lower than those of normal Caucasians by 0.115 ±0.023 in male, and 0.091 ±0.005 in female. 5. We belive that bone densitometer is an effective tool in early detection and treatment in metabolic bone deseass including osteoporosis.