Before carrying out any action, whether it is concerned with professional life or with humdrum everyday routine, one has always to choose between at least two alternatives: to act or not to act. Decisions are always based upon information, and it is clear that this information should be of the best quality possible and that it should also be used in the most efficient way possible. Judgement analysis helps to improve the reliability of clinical decisions, in practice as well as in the management of clinical trials.