2 years after successful organization of the first World Congress on Social Simulation, George Mason University (USA, Washington DC) hosted the second Congress on July 14-17, 2008. The Congress was sponsored by three regional associations, specializing in social modeling: North American Association for Computational Social and Organizational Sciences (NAACSOS), European Social Simulation Association (ESSA), Pacific-Asian Association for Agent-based Approach in Social Systems Sciences (PAAA).