Within the Dutch BAZIS cooperation of 25 major hospitals the IMAGIS (Image Information System) project was started in 1984 to realize a working PACS (Picture Archiving and Communication System) prototype in the next few years. Such a prototype should be clinically evaluated primarily at the Utrecht University Hospital. Simulation has been chosen as a major tool for the set-up and study of a future medical PACS in Dutch hospitals. A pilot study conducted by us thusfar has indicated the usefulness of simulation for our purposes, and clearly indicated the need for information on the present use of images within both the radiological department and the hospital as a whole. We use two ways to collect these data. The first way is through a rough (written) inquiry to all participating hospitals. This will immediately be followed by a more detailed questionnaire to the most involved participants of the BAZIS organization. The second way of collecting crucial data is through a thorough observation of the image handling processes at the Radiology Departments of the Leiden and Utrecht University Hospitals. As may be expected, there will be quite some differences between university (teaching) hospitals and general hospitals, which we will take into account for the Dutch situation. The simulation model that is being extended now will be based upon our inquiry and observation results. The model will include as much components as feasible. Among these will be control layers, interfaces to the existing HIS, a multi-level archive, various numbers and types of imaging workstations, connected by different networks for images, graphics and text, each with specific requirements concerning media, speed and topology. Our final aim is twofold: the study of imaging procedures in existing hospitals and hospitals under construction, and the simulation and the realization of a feasible complete IMAGIS, evolving from a number of successive prototyping iteration cycles.