Since the first edition, the research literature on aging continues to expand rapidly, reflecting both the rising interest of the scientific community and also the needs of a growing older population. In the year 1900, persons over 65 years of age were the smallest portion of developed societies. Today they are emerging as the largest. Aging is a complex process of change involving influences of a biological, behavioral, social, and environmental nature, all of which are explored in the context of this encyclopedia. The second edition includes all new articles and wholly new coverage of topics that have seen research advances. The Second Edition will be available online via our ScienceDirect platform in early 2007. Online version is priced separately.