Quantitative computed tomography (QCT) provides three-dimensional information about bone geometry and the spatial distribution of bone mineral. Images obtained with QCT can be used to create finite element models, which offer the ability to analyze bone strength and the distribution of mechanical stress and physical deformation. This approach can be used to investigate different mechanical loading scenarios (stance and fall configurations at the hip, for example) and to estimate whole bone strength and the relative mechanical contributions of the cortical and trabecular bone compartments. Finite element analyses based on QCT images of the hip and spine have been used to provide important insights into the biomechanical effects of factors such as age, sex, bone loss, pharmaceuticals, and mechanical loading at sites of high clinical importance. Thus, this analysis approach has become an important tool in the study of the etiology and treatment of osteoporosis at the hip and spine.