This study was conducted to investigate osteopenia and osteoporosis prevalence of radius and tibia using Quantitative Ultrasound (QUS) and to identify affecting factors of osteoporosis. A total of 4,340 women aged 40 - 69 years, living in Ansung (rural) and Ansan (mid-sized) area, and free of illnesses affecting bone metabolism participated in the community-based cohort study. Among them 4,059 subjects measured radius bone density and 4,089 measured tibia. The T-score threshold, defined as < -1.0 and < or = -2.5, was used to identify subjects with osteopenia and osteoporosis by WHO criteria. The crude prevalence of osteoporosis in radius and tibia was 8.4% and 23.3% respectively; after adjustment for age, it changed 6.3% and 18.8%. In simple logistic regression analysis, the prevalence of osteoporosis increased by aging, non-marital status, low education, low income. Otherwise, high intakes of Ca/P, thiamin, riboflavin, vitamin B6, and vitamin E were decreased osteoporosis prevalence. Compared to the normal BMI (body mass index) group (18.5 < or = BMI < 23), the odds ratio (ORs) of the low BMI group (BMI < 18.5), and high BMI groups (BMI 25 - 30, BMI > or = 30) were significantly increased. The OR of osteoporosis decreased across increasing quartiles of intakes of Ca, P and Ca/P. Therefore, maintaining normal BMI and increasing Ca intake and Ca/P ratio may have a beneficial effect on bone health of Korean women.