This book constitutes the refereed proceedings of the 20th International Conference on Group Decision and Negotiation, GDN 2020, which was planned to be held in Toronto, ON, Canada, during June 7–11, 2020. The conference was cancelled due to the Coronavirus pandemic. Nevertheless, it was decided to publish the proceedings, because the review process had already been completed at the time the cancellation was decided. The field of Group Decision and Negotiation focuses on decision processes with at least two participants and a common goal but conflicting individual goals. Research areas of Group Decision and Negotiation include electronic negotiations, experiments, the role of emotions in group decision and negotiations, preference elicitation and decision support for group decisions and negotiations, and conflict resolution principles. The 14 full papers presented in this volume were carefully reviewed and selected from 75 submissions. They were organized in topical sections named: Conflict Resolution, Preference Modeling for Group Decision and Negotiation, Intelligent Group Decision Making and Consensus Process, Collaborative Decision Making Processes.

This book constitutes the refereed proceedings of the 20th International Conference on Group Decision and Negotiation, GDN 2020, which was planned to be held in Toronto, ON, Canada, during June 7–11, 2020. The conference was cancelled due to the Coronavirus pandemic. Nevertheless, it was decided to publish the proceedings, because the review process had already been completed at the time the cancellation was decided. The field of Group Decision and Negotiation focuses on decision processes with at least two participants and a common goal but conflicting individual goals. Research areas of Group Decision and Negotiation include electronic negotiations, experiments, the role of emotions in group decision and negotiations, preference elicitation and decision support for group decisions and negotiations, and conflict resolution principles. The 14 full papers presented in this volume were carefully reviewed and selected from 75 submissions. They were organized in topical sections named: Conflict Resolution, Preference Modeling for Group Decision and Negotiation, Intelligent Group Decision Making and Consensus Process, Collaborative Decision Making Processes.

Publication of the Handbook of Group Decision and Negotiation marks a milestone in the evolution of the group decision and negotiation (GDN) eld. On this occasion, editors Colin Eden and Marc Kilgour asked me to write a brief history of the eld to provide background and context for the volume. They said that I am in a good position to do so: Actively involved in creating the GDN Section and serving as its chair; founding and leading the GDN journal, Group Decision and Negotiation as editor-in-chief, and the book series, “Advances in Group Decision and Negotiation” as editor; and serving as general chair of the GDN annual meetings. I accepted their invitation to write a brief history. In 1989 what is now the Institute for Operations Research and the Management Sciences (INFORMS) established its Section on Group Decision and Negotiation. The journal Group Decision and Negotiation was founded in 1992, published by Springer in cooperation with INFORMS and the GDN Section. In 2003, as an ext- sion of the journal, the Springer book series, “Advances in Group Decision and Negotiation” was inaugurated.

This book constitutes the refereed proceedings of the 23rd International Conference on Group Decision and Negotiation, GDN 2023, which took place in Tokyo, Japan during June 11–15, 2023. The field of Group Decision and Negotiation focuses on decision processes with at least two participants and a common goal but conflicting individual goals. Research areas of Group Decision and Negotiation include electronic negotiations, experiments, the role of emotions in group decision and negotiations, preference elicitation and decision support for group decisions and negotiations, and conflict resolution principles. This year’s conference focusses on multimodal interactions. The 11 full papers presented in this volume were carefully reviewed and selected from 102 submissions. They were organized in the following topical sections: Taking a step back: Critically re-examining technology interactions with group decision and negotiation; preference modeling and multi-criteria decision-making; and conflict modeling and distributive mechanisms.

This book constitutes the refereed proceedings of the 21st International Conference on Group Decision and Negotiation, GDN 2021, which was planned to be held in Toronto, ON, Canada, during June 6–10, 2021. The conference was held virtually due to the COVID-19 pandemic. The field of Group Decision and Negotiation focuses on decision processes with at least two participants and a common goal but conflicting individual goals. Research areas of Group Decision and Negotiation include electronic negotiations, experiments, the role of emotions in group decision and negotiations, preference elicitation and decision support for group decisions and negotiations, and conflict resolution principles. The 12 full papers presented in this volume were carefully reviewed and selected from 74 submissions. They were organized in topical sections as follows: pandemic responses; preference modeling for group decision and negotiation; conflict resolution; and collaborative decision making processes.

This book constitutes the refereed proceedings of the 17th International Conference on Group Decision and Negotiation, GDN 2017, held in Stuttgart, Germany, in August 2017. The field of Group Decision and Negotiation focuses on decision processes with at least two participants and a common goal but conflicting individual goals. Research areas of Group Decision and Negotiation include electronic negotiations, experiments, the role of emotions in group decision and negotiations, preference elicitation and decision support for group decisions and negotiations, and conflict resolution principles. The 14 full papers presented in this volume were carefully reviewed and selected from 87 submissions. They were organized in topical sections named: general topics in group decision and negotiation; conflict resolution; emotions in group decision and negotiation; negotiation support systems and studies; and preference modeling for group decision and negotiation. The book also contains two invited talks in full paper length.