A serendipitous finding in a study of routine clinical encounters was that physicians and patients frequently gave discrepant reports of what had happened during a clinic visit. This report examines the conditions under which these discrepant perceptions occurred. Five experienced physicians and 189 patients completed postencounter questionnaires immediately following visits to an academic family practice clinic. After each encounter, the physician and patient estimated the duration of the visit and reported whether each of seven clinical events had occurred. The most common disagreements concerned whether the physician had provided counseling or performed a treatment procedure. Multiple regression analyses suggest that patient characteristics contributed to specific forms of physician-patient disagreement but that overall discrepancy was greatest in cases in which the physician minimized the importance of psychosocial issues and/or felt relatively confident about understanding the patient's problem. Although correlation need not imply causality, the results raise the possibility that physicians can promote shared physician-patient understanding by paying more attention to psychosocial factors and being more circumspect in drawing conclusions about patients' problems.