The Fourth World Congress on Social Simulation was held in Taipei, Taiwan on 4-7 November 2012. It was jointly organised by PAAA (Pacific and Asia), CSSSA (North America) and ESSA (Europe). It was co-sponsored by National Science Council, Bureau of Foreign Trade and National Chengchi Univ.& College of Social Science. Invited speakers were Alan Kirman (University of Aix-Marseille III, France), Kumaraswamy (Vela) Velupillai (University of Trento, Italy), Thomas Lux (University of Kiel, Germany), Wei Zhang (Tianjin University, China) and William Griffin (Arizona State University, USA).