The field of Group Decision and Negotiation can be described as the empirical, formal, computational, and strategic analysis of group decision-making and negotiation, especially from the points of view of Management Science and Operations Research. Group Decision and Negotiation crosses many traditional disciplinary boundaries, and has connections to business administration and business strategy, management science, systems engineering, computer science, mathematics, and law, as well as economics, psychology, and other social sciences. The Handbook of Group Decision and Negotiation is intended to become the major reference in the field. The only current references are the highly successful journal Group Decision and Negotiation, as well as the books of the Advances in Group Decision and Negotiation series, and a few other journals. Researchers, students, and practitioners in this growing field sorely need a good general reference.