In the last several years, many new techniques have been introduced for the measurement of bone density. At present, the clinician is faced with a choice between various technologies that provide measurements of different skeletal sites. Each of these techniques offer advantages and disadvantages for clinical use. Currently, no single technique ideally addresses all clinical requirements. Although all bone density techniques have clinical utility for assessing fracture risk, some devices offer advantages in terms of versatility (i.e., the number of skeletal sites which can be measured), ability to monitor response, cost, availability, and ease of use. Still, the question often is asked, which technique is the best to use? In clinical practice, the answer to this question will depend on the purpose of the bone density measurement. Different indications for bone mass evaluation will necessitate the measurement of different skeletal sites, which will in turn dictate which technique should be ideally used. In this article, the common clinical questions surrounding bone density measurements are reviewed, together with data supporting the appropriate skeletal site to measure to best answer these clinical questions.