This thesis is about simulations in professional education and what they mean for developing professional knowing. When educating new police officers, using simulations is an integral part of the educational program. A starting point for the studies in this thesis was that not only the scenario but also the preparation and the debriefing, i.e. the situated activities, must be included. Another starting point was that activities and the individuals cannot be studied separately; both have to be included in the analyses. Two simulations, which were part of the Swedish police education program were studied. The approach was explorative and the methods used to collect data were observations, video-observations, interviews and surveys. The unit of analysis focused how students acted in and how they made sense of the simulation activities. The analytical process was influenced by a sociocultural and dialogical framework, in which learning is seen as a social activity. The thesis showed that using simulation in professional education is a complex endeavor in which the social aspects of simulating have to be acknowledged. The analyses showed that the situated activities of the simulation have to be linked to each other in way that enables the participants to; first, produce a situation with authenticity and second, to use previous experiences and coordinate them with new ones from the simulation in order to create good conditions for learning. This means acknowledging that the stance of a simulation needs to be longer than just the actual simulation. How they are embedded in the education program and how gaps in students knowing are to be bridged after the simulation, need to be considered. The main implication of the results is that the use of simulations in professional education require a specific simulation pedagogy. Some foundations of this are outlined and include; the fact that a simulated situation is a hybrid and never a mirror of a professional situation and also includes creating simulation competence among both teachers and students. This includes learning the “gaming rules” of simulating such as how to act in different roles, how to produce authenticity, what is to be included and what is to be ignored in order to make the scenario work. Simulation pedagogy also has to acknowledge that focus needs to be on how to support the participants’ learning and not assume that there is a direct connection between participation and learning. If all of these issues are considered in the design, the potential of simulations for developing professional knowing can be utilized. To conclude, this thesis shows that in the detailed study of scenarios, preparation and follow-up are important and draw attention to aspects that are central for understanding the conditions for learning in simulations.