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. This workshop was the third in the MABS series. The earlier two were - ganized as workshops of the two most recent ICMAS conferences (ICMAS 1998, Paris, France and ICMAS 2000, Boston, USA). Revised versions of the papers presented at these workshops were published as volumes 1534 and 1979 in the Lecture Notes in Artificial Intelligence series. One aim of the workshop was to develop stronger links between those wo- ing 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 - clude 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, or- nizational 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.