The objectives of this study were to determine factors related to fractures and bone mineral density (BMD) in a large group of Norwegian women. In a cross-sectional study, 3803 women aged 50-75, all with a history of fractures, were included in the study. BMD was measured with Dual energy X-ray absorptiometry at both hip (neck) and spine (L1-L4), while information on other factors thought to influence BMD were obtained through a questionnaire. In multivariate analysis, the strongest positive predictor of both hip and spine BMD was current body weight, while weight loss since the age of 25 and number of years since menopause were the strongest inverse predictors. In addition, use of cortisone and maternal history of fractures were associated with lower BMD, as was loss of height since the age of 25. Physical activity was positively correlated with BMD. These results show the complexity of factors involved in the etiology of osteoporosis, with several factors acting in synergism. This points to the need for multifactorial prevention strategies, which most effectively need to be instituted at an early age, before peak bone mass is achieved.