There is no question that simulation can be an effective tool for training complex skills. There is some evidence that it works.1 But it is only a tool. As with any tool, in order to be effective it must be used appropriately. We commend the paper by Satish and Streufert2 in this issue of QSHC for highlighting the role that simulation may play in both training and assessment within the medical community, as well as the recognition that effective simulation must: (1) be built on underlying theory (they use complexity theory), (2) use structured exercises, and (3) assess performance and provide feedback. However, some additional observations about simulation are warranted so that scientists and training developers within the medical community do not fall into some common myths and misconceptions known to exist regarding training in general, as well as the use of simulation for training.3 We therefore present a few observations based on the science of training1,4 and our experience in aviation and military environments about when simulation is effective for training.5,6 Simulation for training is effective when …