This study is an investigation of the existence and potential causes of systematic differences between patients and physicians in their assessments of the intensity of patients' pain. In an emergency department in France, patients (N=200) and their physicians (N=48) rated the patients' pain using a visual analog scale, both on arrival and at discharge. Results showed, in confirmation of previous studies, that physicians gave significantly lower ratings than did patients of the patients' pain both on arrival (mean difference -1.33, standard error (SE)=0.17, on a scale of 0-10, P<0.001) and at exit (-1.38, SE=0.15, P<0.001). The extent of 'miscalibration' was greater with expert than novice physicians and depended on interactions among physician gender, patient gender, and the obviousness of the cause of pain. Thus physicians' pain ratings may have been affected by non-medical factors.