Measurement of bone mineral density (BMD) is used to diagnose osteoporosis, assess fracture risk, and monitor response to therapy. Of the different methods for measuring BMD, dual-energy X-ray absorptiometry (DXA) is the only technology for classifying BMD according to criteria established by the World Health Organization (WHO) and the only technology that is validated for BMD input with the WHO fracture risk assessment algorithm, FRAX. Vertebral fracture assessment (VFA) by DXA provides an image of the thoracic and lumbar spine for the purpose of detecting vertebral fracture deformities. Identification of a previously unrecognized vertebral fracture may change diagnostic classification, assessment of fracture risk, and treatment decisions. In comparison with standard radiographs of the spine, the correlation for detecting moderate and severe vertebral fractures is good, with a smaller dose of ionizing irradiation, greater patient convenience, and lower cost. Optimal performance of DXA and VFA requires training and adherence to quality standards.