The Fourth ESSA Summer School in Social Simulation was held in Hamburg, Germany on 15-19 July 2013. The programme consisted of lectures from experienced social simulation modellers, student group work and practice. The Faculty included Nigel Gilbert (University of Surrey, UK), Klaus G. Troitzsch (University of Koblenz-Landau, Germany), Scott Moss (Metropolitan Manchester Business School, UK) and Mathias Meyer (Hamburg University of Technology, Germany), among others.