The present volume of Springer’s \Lecture Notes in Arti cial Intelligence" - cuses on the challenge of balancing between the two extremes of pure reactivity and in-depth social deliberation in the context of multi-agent systems. Finding a balance between these two extremes will lead to an overall behavior of the individual agents and of the multi-agent system that meets the demands of the environment but also the demand for high-quality problem solving results. This book collects selected and revised papers from \Balancing Reactivity and Social Deliberation in Multi-Agent Systems"{aworkshop held at the 14th European Conference on Arti cial Intelligence (ECAI 2000) { and additional papers from renowned researchers in the eld. All the papers contained in this book have undergone at least one complete phase of reviewing and correction with ty- cally three reviews, the large majority of them have been through two phases. In the rst phase, papers were reviewed by members of the advisory committee, in the second phase, papers were peer-reviewed among the authors with additional comments from members of the advisory committee. Although several contributions to this book stem from members of the - boCup community and as such also deal with related topics, this is not a book on RoboCup.