After the huge success of the ?rst German Conference on Multiagent System Technologies (MATES) last year in Erfurt the German Special Interest Group on Distributed Arti?cial Intelligence together with the steering committee of MATES proudly organized and conducted this international conference for the second time. ThegoaloftheMATESconferenceistoconstituteahigh-qualityplatformfor thepresentationanddiscussionofnewresearchresultsandsystemdevelopments. It provides an interdisciplinary forum for researchers, users, and developers, to present and discuss the latest advances in research work, as well as prototyped or?eldedsystemsofintelligentagents.Theconferencecoversthecompleterange from theory to application of agent and multiagent technologies. MATES 2004 was conducted - asanintegralpartofthe5thInternationalConferenceNet.ObjectDays2004 along with the - 8th International Workshop on Cooperative Information Agents (CIA) 2004 - Autumn meeting of FIPA (Foundation for Intelligent Physical Agents) - PrototypeandProductExhibitionofAgentRelatedPlatforms,Frameworks, Systems, Applications, and Tools As such all these events together may have formed the biggest agent-related event of this year in Europe and one of the biggest worldwide.The call-for-papers attracted about 60 submissions from all over the world. After a carefulreviewing process,the internationalprogramcommittee accepted 22 high-quality papers of particular relevance and quality. The selected cont- butions cover a wide range of exciting topics, in particular agent analysis and security, agent negotiation and control, agents and software engineering, s- ulation and agents, and agent policies and testing. Exciting highlights of the conference were the invited talks, by Jim Odell on Agent UML 2.0: Too Radical or Not Radical Enough?, and Cristiano Castelfranchi on Emergence and C- nition: Towards a Synthetic Paradigm in AI and Cognitive Science.Moreover, several agent-related tutorials were conducted.