This volume presents extended and revised versions of the papers presented at the Third International Workshop on Multi-Agent Based Simulation (MABS 2002), a workshop federated with the First International Joint Conference on Autonomous Agents and Multi-Agent Systems (AAMAS 2002), which was held in Bologna, Italy, in July, 2002. One aim of the workshop was to develop stronger links between those working in the social sciences and those involved with multi-agent systems. We are pleased to note that many important conferences in various disciplines such as geography, economics, ecology, sociology, and physics have hosted workshops on MABS-related topics and that many respected journals publish papers that include elements of MABS. But although MABS is gradually acquiring legitimacy in many disciplinary fields, much remains to be done to clarify the potential use of MABS in these disciplines. Researchers from these disciplines have different points of view on issues such as time-frame, space, geographical scales, organizational levels, etc. Moreover, the interest in MABS goes beyond the scientific community, as MABS models have been developed and used interactively with other communities as well. For instance, research is being done on the interactions between societies of robots and groups of people, and simulation models are being developed with stakeholders for environmental issues in a participatory way, through the Internet or directly in the field. These new approaches lead to new research questions regarding the use of MABS for collective decision making, but also regarding the conceptual and technical aspects of MABS. Within this framework of interactions between artificial and human societies, special attention was given to the conceptual and technical aspects (agent architecture, interaction protocols, simulation platforms, modeling protocols, time and space representation, presentation of simulation results) resulting from these interactions and favoring the