ABSTRACT: BACKGROUND: Epistemological beliefs (EB) are an individual's cognitions about knowledge and knowing. In several non-medical domains, EB have been found to contribute to the way individuals reason when faced with ill-structured problems (i.e. problems with no clear-cut, right or wrong solutions). Such problems are very common in medical practice. Determining whether EB are also influential in reasoning processes with regard to medical issues to which there is no straightforward answer, could have implications for medical education. This study focused on 2 research questions: 1. Can ill-structured problems be used to elicit general practice trainees' and trainers' EB? and 2. What are the views of general practice trainees and trainers about knowledge and how do they justify knowing? METHODS: 2 focus groups of trainees (n=18) were convened on 3 occasions during their 1st year of postgraduate GP training. 2 groups of GP trainers (n=11) met on one occasion. Based on the methodology of the Reflective Judgement Interview (RJI), participants were asked to comment on 11 ill-structured problems. The sessions were audio taped and transcribed and an adapted version of the RJI scoring rules was used to assess the trainees' reasoning about ill-structured problems. RESULTS: Participants made a number of statements illustrating their EB and their importance in clinical reasoning. The level of EB varied widely form one meeting to another and depending on the problem addressed. Overall, the EB expressed by trainees did not differ from those of trainers except on a particular ill-structured problem regarding shoulder pain. CONCLUSIONS: The use of focus groups has entailed some difficulties in the interpretation of the results, but a number of preliminary conclusions can be drawn. Ill-structured medical problems can be used to elicit EB. Most trainees and trainers displayed pre-reflective and quasi-reflective EB. The way trainees and doctors view and justify knowledge are likely to be involved in medical reasoning processes.