Precision and accuracy are terms that are used in quantitative scientific fields to describe the reproducibility of a measurement or the capacity of a measurement to quantify the actual biological matter present. Precision and accuracy are also important applications in the quality control and quality assurance of the performance and interpretation of bone mass measure­ ments. Precision and accuracy also reflect the values and qualities of the author of this important text in the clinical application of bone densitometry. This is the first textbook of its kind devoted entirely to the proper use of this technology in the practice of medicine. Dr. Sydney L. Bonnick has devoted a majority of her career helping to define excellence in this exploding area and in doing so, has earned the respect and admiration of the international bone densitometry community. Confusion abounds in this field due to the proliferation of bone densito­ metry devices, including the various models that can measure many skel­ etal sites, the different normative data bases used, and the establishment of diagnostic categories of low bone mass. Dr. Bonnick's authoritative and carefully referenced text will certainly clarify and broaden the knowledge of those physicians who currently perform bone densitometry. This text is designed to be utilized by a wide range of medical specialists: endocrinolo­ gists, rheumatologists, gynecologists, radiologists, orthopedic surgeons, and nephrologists.