Introduction: Teaching of physiology to undergraduate students is prerequisite to successful education in a number of disciplines. In acute care medicine but also in other fields, good understanding of physiology can make the difference between life and death or severe injury. Especially in medicine the term simulation is ill-defined. Also adjectives, like “high fidelity”, are used in arbitrary fashion. In the present context I will call high fidelity simulator an educational device that uses a mathematical model of physiology to control a mannequin with sensors and actuators that resembles a human being. Teachers and students can access both mannequin and software to influence physiological data and observe the results. I exclude screen based-only devices or mannequins without mathematical model. High fidelity simulators are in use around the world. Although physiology is the core of these devices, they seem to be used most often in clinical trainings. But a number of institutions are teaching “pure” physiology with high fidelity simulators and this number is growing. Existing teaching programmes: There is no geographical limitation to physiology teaching with high fidelity simulators, e.g. the U.S., New Zealand, Singapore, Germany and the United Kingdom have sites which teach with simulators. Typical teaching topics are: The baroreceptor reflex and its components, respiratory control, katecholamines, oxygen binding curves, respiratory shunt fraction, functional residual capacity, and others. However, a number of sites are using their high fidelity simulators not in “official” physiology courses but rather in anaesthesia, intensive care, emergency medicine and other fields of acute care. Theses fields could be summarized as applied physiology. While in such undergraduate trainings the official headline may be e.g. “anaesthesia” rather than “physiology”, the latter is really what is taught. In these cases the clinical training is a method to re-learn physiology in the context of practical use. Typical topics then are: The effect of blood loss and volume replacement on circulation in trauma victims, cardiac output measurement, the interpretation of SpO2 monitor readings, the relationship between pre-oxygenation and age, the use of PEEP etc. In “pure physiological” contexts the training allows to conduct experiments which are less and less acceptable on animals. In clinical trainings, high fidelity simulators very often replace the use of patients to gain experience. Simulation programmes, similar to all teaching programmes are often “home made”. In many institutions rules on curriculum development and knowledge about education methodology are lacking. Even centres with better conditions often lack resources to re-develop their existing programmes to be run with simulators. In these cases high fidelity simulation may not generate large benefit or may even fail. It would be very desirable to be able to tap into the growing number of prepared learning packages for high fidelity simulators also in physiology. Discussion: All new teaching methods are subject to scrutiny with respect to effect and efficacy. While we do not really know how well our traditional methods work, it is correct to measure the effects of high fidelity simulation, not least because it requires the allocation of resources. A growing number of references point into the same direction: Teaching physiology with high fidelity simulators can be beneficial. It may be argued that software programmes can be used solely to replace animal experiments. I think that these programmes lack what the mannequins offer in high fidelity simulation: The opportunity to experiment and to gain in experience. Adult learning seems to work well with experiential learning and mannequins controlled by mathematical models provide it. While on one hand high fidelity simulators invite to experiment freely, they provide also a standardized setting when needed. Pre-programmed cases, re-usable scripts, technical specifications all help to make learning experiences on a high fidelity simulator repeatable. This is important in learning but also for assessments. The opportunity to automatically log and recall physiological data and the added benefit of videos make it possible not only to judge the outcome of an experiment. Rather, these tools also allow the analysis of how the experiment developed. In case of physiology they offer the unique opportunity to video-debrief a process, thus even improving the experiential learning process. Based on almost 15 years of clinical experience in acute care I know that knowledge in physiology is sometimes in short supply in applied medicine. High fidelity simulators may be the tool we need to improve this knowledge which is prerequisite to improve patient safety.