This study was conducted to investigate the effect of physiological and behavioral factors on the bone density of 125 middle aged women who visited Saint Bundo Hospital. 16.1% of subjects had osteoporosis and 40.3% had osteopenia according to the measurement of the bone density of lumbar spine. Mean age was 56.9 in osteoporosis group and 53.7 in osteopenia group. It was significantly different from the mean age of control group, 50.7. The mean bone density of the women who had menarche after 15 years old was significantly lower than that of the women who had menarche before 15. But the age of menopause, the total year of menstruation, irregularity of the menstrual cycle and percentage of subjects who had ovariectomy were not significantly different among osteoporosis, osteopenia and control group. The use of medication such as oral contraceptive, steroid, depressant, diuretic, and Ca supplement and the preference of salty food were not significantly different among three groups. The percentage of subjects who had rheumatism, gastric ulcer, and pain in neck or shoulder was higher in osteoporosis and osteopenia group than in control group. This study shows that the age and the age of menarche affect the bone density, and that behavioral factors were not sig nificantly different in osteoporosis and osteopenia group compared to the control group. Further researches are needed to find out the effective way to minimize the effect of age and other physiological conditions on the decrease of bone density.