The publication of this unique three-volume set represents the culmination of years of work by a large number of scholars, researchers, and professionals in the field of moral development. The literature on moral behavior and development has grown to the point where it is no longer possible to capture the “state of the art” in a single volume. This comprehensive multi-volume Handbook marks an important transition because it provides evidence that the field has emerged as an area of scholarly activity in its own right. Spanning many professional domains, there is a striking variety of issues and topics surveyed: anthropology, biology, economics, education, philosophy, psychology, psychiatry, sociology, social work, and more. By bringing together work on diverse topics, the editors have fostered a mutually-beneficial exchange not only between alternative approaches and perspectives, but also between “applied” and “pure” research interests. The Theory volume presents current and ongoing theoretical advances focusing on new developments or substantive refinements and revisions to existing theoretical frameworks. The Research volume summarizes and interprets the findings of specific, theory-driven, research programs; reviews research in areas that have generated substantial empirical findings; describes recent developments in research methodology/techniques; and reports research on new and emerging issues. The Application volume describes a diverse array of intervention projects — educational, clinical, organizational, and the like. Each chapter includes a summary report of results and findings, conceptual developments, and emerging issues or topics. Since the contributors to this publication are active theorists, researchers, and practitioners, it may serve to define directions that will shape the emerging literature in the field.