BACKGROUND: The improvement in social economic standard of living and aging bring high attention to osteoporosis in women. Many studies have been released so far about how effectively Hormone Replacement Therapy(HRT) in postmenopausal women works for the increase in Bone Mineral Density(BMD) in hip and vertebrae with the different rate of bone formation. In addition, it has been believed that HRT could increase BMD of hip and lumbar vertebrae reduce fractures caused by osteoporosis. In this study, we will find the effect of HRT on the increase in BMD of lumbar vertebrae and hip in postmenopausal women, by measuring and comparing BMD of lumbar vertebrae with high rate of trabecular bone to that of hip with high rate of cortical bone one year after HRT in postmenopausal women. METHODS: Subjects were 48 out of 325 postmenopausal women patients who visited osteoporosis clinic, Sun Hospital, Taejeon, from January, 1995 to December, 1995 and had the osteoporosis test and the vertebrae osteoporosis test one year after. We compared and analyzed the change of BMD in each part by retesting BMD of lumbar vertebrae and hip one year after the continuous HRT in women. SPSS/PC was used for statistical procedure. RESULTS: Subjects have mean age of 54.8+/-4.5 years, mean menopausal age of 48.4+/-3.5 years, mean postmenopause period of 6.5 +/- 5.9 years, mean body mass index 23.4+/-3.1kg/m2, mean weight of 56.7 +/- 7.8kg and mean height of 154715.4cm. No correlation was observed of their age, menopausal age, the number of years since menopause and body mass index to the changing rate of BMD in lumbar vertebrae and femur one year after HRT in women. The BMD prior to treatment was, respectively, as follows , L2-L4(0.8983710.llg/cm2), Hip(neck, 0.7597+/-0.10g/cm2 ; trochanter, 0.6259+/-0.08g/cm2 ; Ward's triangle,0.5186+/-0.90g/cm2), and that one year after treatment ; L2-L4(0.9277+/-0.llg/cm2), Hip(neck,0.7592710.llg/cm2 ; trochanter, 0.63227:0.08g/cm" ; Ward's triangle,0.5340+/-0.09g/cm2). There was significant increase in BMD of lumbar vertebrae and femur Ward's triangle(P<0.01) among BMD of each part one year after HRT, but BMD of femur neck and that of trochanter region has no significant incense. CONCLUSIONS: It was found that one year treatment with HRT in postmenopausal women resulted in significant increase in BMD of not only lumbar vertebrae with lots of trabecular bone but also Ward's triangle regions of femur, regardless of age and postmenopausal period of postmenopausal women at the beginning of treatment. It is considered that HRT may be effective in preventing osteoporotic fractures of lumbar vertebrae and hip on postmenopausal women, and that postmenopausal period would not be an important factor in the beginning of HRT treatment.