PURPOSE: The purpose of this study was to show how bone mineral densities of the lumbar spine decrease with aging, to investigate the relationship between the bone mineral densities of the control and fracture group, and to obtain fracture threshold values. MATERIALS AND METHOD: From January 1995 to December 1999, we measured and evaluated BMD of L3 by DXA in 239 normal volunteers(96 men and 143 women), and in 218 patients with lumbar spine fracture(91 men and 127 women) above 50 years. The Chi-Square test was used for statistical analysis. RESULTS: 1. The average BMD of L3 in control group and lumbar spine fracture group were 0.772±0.030 g/cm2 in male and 0.732±0 . 0 8 9 g / c m2 i n female and 0.720±0 . 0 3 1 g / c m2 in male and 0.692±0 . 0 0 2 g / c m2 i n female, respectively. RESULTS: 2. The BMD of the control group and fracture group decreased with aging(p<0.05) and were higher in men than in women. There were statistically significant difference(p<0.001). RESULTS: 3. There were statistically significant difference between BMD of the control group and BMD of the lumbar spine fracture group(p<0.05). The BMD were higher in the control group than fracture group. RESULTS: 4. Fracture threshold of the lumbar spine fracture group were 0.867g/cm2( male: 0.898g /cm2, female:0.836g/cm2) according to 90 percentile.