Medical informatics as a medical discipline has developed over the last decades in parallel with an even more amazing proliferative development in medicine. The question is raised whether this new science, based on formalized and methodological approaches, may contribute to the development of a general theory in medicine as a consequence of the recognition of the influence of control mechanisms and structured information in molecular biology. It is suggested that medical informatics dedicates research to problems 'inside medicine' and that curricula are developed which bring a basic understanding for medical informatics to the medical student. The following teaching is suggested: basic mandatory courses, electives and inclusions of aspect of medical informatics in the various parts of clinical teaching. The possibility is discussed that the resulting teaching approaches may also be used to convey knowledge in medicine: teaching concepts versus teaching details. Finally, a description of the functional topology of expert systems as they develop is attempted and brought into relation to the architecture of hospital information systems. The increasing importance of expert systems also raises the question of 'decisional trials' as verification procedures when these new tools enter medical practice.