This paper questions the idea that expert doctors use the hypothetico-deductive method when developing diagnoses of routine clinical cases. Up to now, this has not been justified by empirical evidence but by two indirect arguments. The first is that it is the standard procedure of scientific method. The second is that it is supported by research in cognitive psychology comparing the problem-solving behaviour of experts and novices. It is argued in this paper that both areas have been misinterpreted. In particular, the evidence from research in cognitive psychology on expert-novice comparisons indicates that the use of the hypothetico-deductive method is a characteristic of novices rather than experts. Experts use what are called strong methods, which are dependent on a highly elaborated and structured knowledge base. It is concluded that a considerable amount of research on the nature of such strong methods in expert clinical reasoning is needed before any confident claims can be made regarding the use of the hypothetico-deductive or any other method.