The study of complex systems is growing rapidly and modelling and simulation tools are an important part of the process. This volume brings together work from a multidisciplinary group of scientists, who are studying a variety of techniques and applications for modelling and simulating complex systems. Building on the success of the 2008 and 2009 CoSMoS workshops, the work presented covers subjects ranging from philosophy, scientific validity, and the modelling and simulation of biological and socio-technical systems.