A suitable General Architecture for Medical Expert Systems (GAMES) has been defined in terms of generic tasks (diagnosis, therapy planning and monitoring) to be executed for developing medical reasoning in a patient's management. Their epistemological structure has been investigated. The GAMES project aims at designing a general architecture for knowledge based systems in medicine. The focus of the project is on the comparison and validation of different approaches in order to implement the generate and test cycle, which represents the basic feature of the epistemological model of medical reasoning we developed.