OBJECTIVES To investigate cognitive schemas and schema systems used by hospital doctors to influence prescribing, particularly in terms of making appropriate prescribing decisions, and to compare the numbers and content of schemas between doctors with different levels of experience. DESIGN Qualitative interviews with a purposively selected sample. PARTICIPANTS AND SETTING Seven pre-registration (PRHOs) and 5 senior house officers (SHOs) and 5 consultants from a range of medical specialties in a teaching hospital. RESULTS The qualitative analysis of the themes and patterns explored during the interviews indicated that all doctors articulated schemas that influenced their behaviour. The junior doctors seemed to have simplistic schemas, with interdoctor agreement; the consultants appeared to have more sophisticated schemas, with greater individual variation. Those schemas adopted by the PRHOs (prescribing 'novices') could be subsumed by, rather than contradicted by, those of the consultants (prescribing 'experts'), with a transitional stage demonstrated by the SHOs. The most noticeable distinction was the greater emphasis by consultants on holistic patient care and what might be seen as their separate schemas for appropriate prescribing stemmed from that premise. In contrast, junior doctors appeared to have had a single schema that encompassed both prescribing generally and appropriate prescribing. CONCLUSIONS Although the design of this study was cross-sectional rather than longitudinal, the findings suggest that the acquisition and adjustment of schemas and schema systems are significant factors in the professional development of the hospital doctor from novice through to expert. It could be hypothesised that house officers possess simpler schemas as a way of coping with their job demands, which evolve in complexity as they gain experience. However, the transitional stage found with the SHOs is critical during cognitive development, with implications for the training and support available to doctors throughout their professional careers.