Unlike dual x-ray absorptiometry and high-resolution CT scan and MR imaging techniques, which are largely restricted to the peripheral skeleton owing to radiation dose and signal-to-noise considerations, volumetric quantitative measures provide measures of cortical and trabecular volumetric bone mineral density, cross-sectional geometry, and estimates of whole-bone strength based on patient specific finite element modeling. This article focuses on the application of volumetric quantitative measures to studies of aging, disuse, and drug treatment as related to osteoporosis.