BACKGROUND: The current evidence on effect of fluoridation in drinking water on bone is inconsistent. This study was undertaken to assess the effect of fluoride concentration in drinking water on bone mineral density (BMD) in Taiwanese women. METHODS: The study subjects included 248 women aged > or = 40 years who reside in naturally fluoridated and adjacent areas. The individual fluoride concentration of the drinking water and the BMD of the subjects’ lumbar spines were assessed. RESULTS: Women aged 46-65 years living in areas which have fluoride levels < 0.6 mg/l (mean = 0.18 mg/l; n = 130) had slightly lower bone densities than women living in areas with levels > or = 0.6 mg/l (mean 0.98 mg/l, n = 118). Only the age groups 46-50 and 61-65 years proved to be statistically significant. After controlling for age and body mass index, the BMD of those who had a dose > or = 1.0 mg/l is notably higher than the reference group (< or = 0.6 mg/l). After stratification by menopausal status, fluoride appeared to have no association with bone density in postmenopausal women. CONCLUSIONS: The BMD of the subjects from the area with a fluoride dose > 1 mg/l were significantly higher than those from the reference group (fluoride < 0.6 mg/l) for premenopausal women. There is no significant association between BMD and fluoride for postmenopausal women in Taiwan.