This volume is based on papers accepted for the Second International Workshop on Multi-agent-based Simulation (MABS-2000)federated with the Fourth Int- national Conference on Multi Agent Systems (ICMAS-2000)held in Boston in July 2000. The purpose of MABS-2000 was to investigate and develop the synergy - tween software engineering for multi-agent systems and agent-based social s- ulation. The papers included in the MABS-2000 workshop were selected either because they explore how agent interaction can be used to build multi-agent systems or they offer examples of problem-oriented (rather than technique-oriented) systems. No paper was selected if it specified a model or an issue to make it—t a previously chosen technique. All of the papers in the volume have been reviewed and in many cases revised since the workshop. Two papers (by Edmonds and by Hales)as well as the editorial introduction have been added to those accepted for the workshop. As editors and workshop organisers, we are very grateful to the participants who engaged enthusiastically in the discussions about both individual papers and the issues facing the MABS community. Issues raised and positions taken in those discussions are reported in the editorial introduction. We are also grateful to the authors for their punctuality and the grace with which they received and responded to editorial comments and requests. Klaus Fischer, the ICMAS-2000 workshops chair, was exceptionally patient and diplomatic in reconciling our demands with the resources available.