Quantitative computed tomography (QCT) is an established technique for measuring bone mineral density (BMD) in the axial spine and peripheral skeleton (forearm, tibia). QCT can determine in three dimensions the true volumetric density (mg/cm 3) of trabecular or cortical bone at any skeletal site. However, because of the high responsiveness of spinal trabecular bone and its importance for vertebral strength, QCT has been principally employed to determine trabecular BMD in the vertebral body. QCT has been used for assessment of vertebral fracture risk, measurement of age-related bone loss, and follow-up of osteoporosis and other metabolic bone diseases. This article reviews the current capabilities of QCT at different skeletal sites and the recent technical developments, including volumetric acquisition.