The field of gerontology has often been criticized for being "data-rich but theory-poor." The editors of this book address this issue by stressing the importance of theory in gerontology. While the previous edition focused on multidisciplinary approaches to aging theory, this new edition provides cross-disciplinary, integrative explanations of aging theory: The contributors of this text have reached beyond traditional disciplinary boundaries to partner with researchers in adjacent fields in studying aging and age-related phenomena. This edition of the handbook consists of 39 chapters written by 67 internationally recognized experts in the field of aging. It is organized in seven sections, reflecting the major theoretical developments in gerontology over the past 10 years.