The goals of this multiauthored book, the first published on the subject, were “to summarize the current state of the art and to identify directions for needed research” and importantly “to examine bone biology and osteoporosis in men in light of how they differ from similar events in women.” The field of bone biology, at the bedside but particularly in the laboratory, has grown tremendously in the last decade, and there is a clear need for a reference source. The editor assembled a panel of experts to expound on a variety of topics, and the book in some respects succeeded in achieving its goals. However, the emphasis of the book is very clinical. It devoted too many clinical chapters to epidemiology, risk factors, and descriptive measurements of bone mass and morphology (which nonetheless are very important) and too few to basic bone biology. Further, a number of chapters were somewhat repetitious and covered similar material such as those on age-related changes in bone remodeling and trabecular architecture and aging and risk factors for low bone mass and risk factors for fractures. It is surprising that a book on bone disease in this day and age would not have one or more introductory chapters on basic bone cell biology that would include descriptions of and methods for evaluating osteoblast and osteoclast function and the microenvironment of the bone marrow, on animal models of osteoporosis including gene knockouts, and on the latest use of techniques of cell and molecular biology to investigate pathogenesis that are being used and how they can be used to expand knowledge in the field. Especially, there is no mention of the Human Genome Project that will shortly make available the structure of all human genes and how this information might be used to make discoveries about the pathogenesis and possibly new treatments for different kinds of osteoporosis. In the 21st century, molecular medicine will no doubt become the standard of care and include new methods for identifying patients at risk for developing bone disease. The goal of investigators will be to discern the role of proteins produced by newly described genes in normal and disease states. Another major omission was the lack of discussion or even mention of the recently discovered osteoclastogenesis stimulating factor/osteoprotegerin ligand and osteoclast inhibitory factor/osteoprotegerin system that has revolutionized our understanding of regulation of bone resorption and has provided a new rationale for developing new and possibly more effective treatments for osteoporosis, Paget's disease, and other diseases. This is especially important in view of the central role of bone resorption in determining bone mass and the rate of age-related bone loss in normal individuals and in individuals with osteoporosis. Despite these criticisms, the chapters that deal with epidemiology, growth, aging, bone mass and morphology, and clinical evaluation are comprehensive and well organized and provide useful comparisons between men and women. There are excellent chapters on exercise, insulin-like growth factors, age-related changes in mineral metabolism, calcium and vitamin D nutrition, androgens, estrogens, idiopathic osteoporosis, glucocorticoids, alcohol, and hypercalciuria. When provided, summaries and directions for future research at the ends of chapters are valuable. In summary, this book provides a useful, well-referenced review of current knowledge of what is known and what is not known relative to osteoporosis in men. If one proposes to use the latest techniques of cell and molecular biology for future investigations, details and description of many of these approaches must be sought elsewhere.