Decision making is of great importance in medicine, and can be analysed according to different theories and research traditions, each with its own criteria for what is meant by a good or correct decision. In classic decision analysis, the criterion is rationality, defined as adherence to logic and probability computation. In clinical judgement analysis, the criterion is agreement with the conditions of external (ecological) reality and how well we adapt to them. According to the naturalistic decision making tradition, there is no better criterion than the opinion of experts in the field. This is discussed in the article, and some of the research traditions are presented.