his volume of the series Lecture Notes in Medical Informatics contains the T proceedings of the Workshop on System Engineering in Medicine, which was held in Maastricht, The Netherlands, 16-18 March 1989. This workshop was sponsored by the EC under the framework of the Medical and Health Research Programme. The aim of the workshop was to assess whether there was sufficient support in the Medical Informatics community in the EC to establish a concerted action. This proceedings contain papers of the presentations given at the workshop. These presentations were centred around three themes: * Methods and Tools * Applications in the domains of chronic care and critical care * Evaluation of decision support systems The papers were prepared after the workshop and therefore we were able to include the relevant parts of the discussions which were related to the presentations. As a result of the discussions during the workshop, a proposal was prepared for the establishment of a concerted action, specifically addressing the development of guidelines for the evaluation of medical decision aids. This proposal was granted early 1990 under the same Medical and Health Research programme of the EC. Over 40 institutes are participating in this concerted action. It have been the outstanding presentations and the open discussions at the workshop that have been the starting point of this concerted action. The papers in this proceedings formed a starting point for the discussions in the meetings of the concerted action.