Basing the prediction of student performance in medical school on intellective-cognitive abilities alone has proved to be more pertinent to academic achievement than to clinical practice. A major obstacle to the development of adequate measures has been the elusive nature of requirements for successful clinical performance. The present study aimed at defining the relevant variables through an analysis of the concept of the medical student held by supervising doctors. With the aid of a methodology derived from cognitive-social psychology, the components of how training doctors of a large medical school evaluate their students were first explicated in structured interviews. In a second phase of the research, 18 supervisors in five major clinical departments rated their student-supervisees on 15 obtained traits. Findings of trait correlations with an overall evaluation, as well as Guttman's 'Smallest Space Analysis' (1968), indicated a clear priority of cognitive-motivational traits in supervisors' judgements and reduced relevance of personal and interpersonal variables. Certain inconsistencies between avowed ideology of medical training and actual supervising practice could be detected.