Until now there are few available epidemiologic data of osteoporosis in Korea, and the severity of osteoporosis-related health problem has not been widely recognized yet. But the numbers of the old people are increasing in Korea, and in 2000, the proportion of people over 65 will be up to about 6.8% of total population. Therefore, osteoporosis, one of the most common metabolic bone disease among the old people, will be one of the most important public health problem. On this background this study was performed to find out risk factors of the development of osteoporosis in Korean women through case-control approach. The subject of this study were selected among the women who visited menopause clinic in one general hospital in Seoul and were checked bone density from Sep. 1988 to Sep. 1993. Those who were diagnosed to have hypertension, diabetes mellitus, thyroid disease, breast disease, or liver disease, which are thought to influnce bone density, were excluded. Also excluded those who are age-unknown. Finally the subjects were 2,139 women aged between 18 and 79. We operatively defined patient group as those whose bone density is below $1.039/cm^2$, 90% of average bone density of women of 4th decade who visited the same hospital. And we defined control group as whose bone dendity is above $1.15g/cm^2$. We randomly selected 201 women from the patient group and 202 from the control. As independent variables we chose age, menarche age, menopause age, menopause type, the number of siblings, the number of pregnancies, body mass index, taking oral pill or not, feeding type, and educational state. Multiple logistic regression analysis was done to see the influence of these variables on the risk of osteoporosis. Results are as follows; 1. menopausal status was statistically significant risk factor to all women irrespective of her age, while obesity and later menopause age were found to be statistically significant protective factors. 2. The more siblings and pregnancies, the greater tile risk of osteoporosis, but these factors were not statistically significant. This result is not consistent with other studies. Further studies are strongly needed.