Third-year medical students used 12 descriptive items to evaluate the teaching skills of first-year residents, senior medical residents, preceptors (internal medicine fellows), and attending physicians. Intraclass correlations showed that the students were able to judge their instructors reliably. Further analyses were then carried out to determine whether students differentially evaluated the four instructor groups. Three of the descriptive items that related to overall evaluations, as well as the mean rating of all items, indicated no group differences. However, when the groups were compared on specific teaching characteristics (by means of a multiple-group discriminant function analysis), systematic differences were found. The first function differentiated the groups in terms of the cognitive and experiential characteristics of the instructors, with attending physicians being rated the highest and first-year residents the lowest. In contrast, the third function separated the groups in terms of interpersonal skills; on this function, the senior medical residents were rated the highest and preceptors the lowest. It is concluded that students make sophisticated judgments in evaluating their clinical teachers.