Current methods for assessing osteoporotic fracture risk involve measuring the content and/or density of bone at a number of skeletal sites and relating the measurement to that in either age-matched or young control subjects measured at the same site with the same technique. These densitometric methods have been used to predict several types of fractures; however, engineering principles verify that the bone structure and loading conditions also affect skeletal strength. Many densitometric measurements inherently contain information about skeletal structure and bone distribution, yet this information is not clinically used. In this paper, the currently available techniques for assessing bone content and density, namely, single-photon absorptiometry, dual-photon absorptiometry, dual-energy X-ray absorptiometry, and quantitative CT, and their usefulness in assessing fracture risk and distinguishing between patients with and without osteoporosis are reviewed. Extensions of conventional densitometry that have ...