The theory of argumentation is a rich, interdisciplinary area of research involving philosophy, communications studies, linguistics, psychology, and logics. Its techniques have found a wide range of applications in both theoretical and practical branches of artificial intelligence and computer science. Multi-agent systems theory has picked up argumentation-inspired approaches and specifically argumentation-theoretic results from many different areas. Researchers in argumentation and multi-agent systems are currently enjoying a unique opportunity to integrate the various understandings of argument into a coherent and core part of the functioning of autonomous computational systems. This book originates from the First International Workshop on Argumentation in Multi-Agent Systems, ArgMAS 2004, held in New York, NY, USA in July 2004. Besides 12 selected revised full papers taken from the workshop, 4 additional papers by key people in the area round off overall coverage of the relevant topics. The papers address the following main topics: foundations of dialogues, belief revision, persuasion and deliberation, negotiation, and strategic issues.