Dietary restriction uniquely and robustly increases maximum lifespan and greatly reduces age-related diseases in many species, including yeast, flies, nematodes, and mammals. To study mechanisms mediating the protective effects of dietary restriction, the National Institute of Aging convened a program involving several leading gerontological laboratories. Results from many of these, as well as from other leading research institutions in the field, are presented in this book. The first three papers address general molecular mechanisms, derived in part from recent DNA microarray studies, that may mediate protective effects of dietary restriction. The subsequent articles examine specific model systems, including flies, nematodes and non-human primates, that have provided exciting new information about these mechanisms. Finally, mechanisms of dietary restriction mediating protective effects against cancer and neurological diseases are discussed. In addition to gerontologists and geriatricians, many other medical and nonmedical professionals in the field will find a great wealth of information on possible interventions that may ameliorate age-related diseases.