With the increasing pace of the knowledge revolution, more and more computer-based tools are becoming available with the potential of assisting and enhancing the processes of decision-making in clinical medicine. If this emergent knowledge technology is to be used to best effect, there is a need to ensure that it is applied in the solution of real clinical problems. This highlights the importance of coupling knowledge technology with a sound systemic framework for problem solving. In this chapter the role of conceptual modelling is described as an aid to understanding the systemic nature of medical and health care situations wherein knowledge technology has a role to play. Issues of systems methodology then arise in relation to this knowledge technology, issues which in some cases parallel those which have already been addressed in relation to dynamic physiological modelling. This interaction of systems thinking and knowledge technology will be illustrated in the context of critical care medicine and diabetes.