In this paper the system-decomposition method is presented, which facilitates the process of modelling of complex systems by multidisciplinary teams. Such modelling is non-trivial, because these teams must codtfy knowledge~omd zflerent scientific disciplines in order to create models that exhibit realistic behaviour. The system-decomposition method has been developed to facilitate the creation of a standard inte$ace for and between researchers, model parts and computer model code. The method was applied to three dzfferent complex system modelling eflorts. The results demonstrate that it reduces modelling costs, improves model quality and enables the integration of knowledge in multidisciplinary teams, the models they produce and the actual written computer code.