Summary.Perceptions by medical students of patients' affective states were investigated, and the effect of the students' own emotions on such perceptions. One hundred and one fourth‐year medical students rated the levels of anxiety and depression of three women patients presented on videotape, rated their own levels of anxiety and depression and completed a questionnaire on aspects of the rating process. Students had widely different and often inappropriate perceptions of patients' levels of anxiety and depression. Students who consistently overrated anxiety or depression in patients, compared to those who consistently underrated, were themselves significantly more anxious or depressed. These data suggest a need in medical education for systematic teaching of empathic skills and for recognition of potential bias in clinical decision‐making arising from the clinician's own emotional st