A complex systems approach to understanding and modelling business marketing systems is described. The focus is on the dynamics and evolution of such systems and the processes and mechanisms driving this, rather than the more usual comparative static, variables based statistical models. Order emerges in a self-organising, bottom up way from the local or micro actions and interactions of those involved. We describe the development of our thinking regarding this approach and its main features, including the development of agent based simulation models and the identification and modelling of underlying mechanisms and processes. We conclude by discussing the implications of this approach for business marketing theory and research.