In the tradition of its preceding meetings, the seventh international conference "Group Decision and Negotiation (GDN) 2006" aims at bringing together researchers in the areas of Group Decisions, Negotiations, and Negotiation Support Systems. Participants share a common research focus on complex decision problems, which involve multiple stakeholders with their sometimes very different interests, as well as the different information, mind-sets, and emotions they bring to the bargaining table. The interdisciplinary research does not only seek to improve our understanding of group decision, negotiations, and market processes, but also to support decision makers, negotiators, and market engineers in achieving better outcomes. The present proceedings outline the results presented at the conference. These range from new economic approaches to advances in information system design.