In this volume, it is attempted to combine two approaches: the first chapters deal with cellular, endocrine, cardiovascular, and neural aging with emphasis on molecular and genetic mechanisms, while the last chapters deal with medical and physciatric interventions. Indeed, the two approaches are not only complementary but they may provide an integrated understanding of the aging process. The elderly are particularly heterogeneous in terms of physiologic competence and pathologic involvement: "successful"aging is clearly distinguishable from "usual" aging. Therefore, progress in molecular biology and genetics can be extremely helpful in indicating appropriate regimens for continuing "wellness" and disease treatment for each aged individual, perhaps more so for the old than for any other age period of the life span. Studies such as the current Human Genome Project are expected to identify genes responsible for rare, obscure diseases and, more importantly, to provide guidelines for optimizing the physiologic potential of all individuals, particularly the elderly. Medicine as it is currently practices may be viewed as a "mass" medicine: everyone receives the same regimen for maintenance of good health and the same treatment for the same diseases. Yet, we know that all diseases do not manifest in the same manner in all individuals, and, in the elderly, symptoms of a given disease often differ markedly from those in the young and adults. Many of these differences depend on the genes with which each individual is born; for example, genes which are adversely affected by excessive smoking or nutrition or lack of physical exercise and poor hygienic habits. The impact of our advancing knowledge of genetics will make it possible to discover which genes are in which form in a particular individual and use this information to refine and individualize prevention and treatment. In other words, in a not too distant future, we may witness a shift from "mass" to "custom" medicine. The individuals most likely to benefit from customized medicine are the elderly, often afflicted simultaneously with multiple diseases and with the side effects of polypharmacy. By presenting a book in which we have included chapters in both basic and clinical studies, we have taken a modest but innovative step toward strengthening communication between molecular and medical sciences.