Quantitative ultrasound (QUS) has been applied to the assessment of bone for almost two decades. The physical interaction of ultrasound and bone is complex and not completely understood. However, it is considered that QUS provides information on bone mass and structure. Although dual-energy X-ray absorptiometry (DXA) is currently considered the "gold standard" for the diagnosis of osteoporosis, through the World Health Organisation definition, there is, in some parts of the world, limited availability to axial DXA. This has stimulated interest in smaller, more portable, and less expensive techniques to indentify those at risk of osteoporotic fracture. One such quantitative method is QUS, which has the added advantage over other photon absorptiometric bone density techniques of not using ionizing radiation. This article reviews the capabilities of QUS and indicates its appropriate application in clinical practice, based on current review of the scientific literature.