Despite its potential influence on quality of care, there has been little research on the way physicians perceptions of and beliefs about patients are affected by patient race or socio-economic status. The lack of research in this area creates a critical gap in our understanding of how patients' demographic characteristics influence encounter characteristics, diagnoses, treatment recommendations, and outcomes. This study uses survey data to examine the degree to which patient race and socio-economic status affected physicians' perceptions of patients during a post-angiogram encounter. A total of 842 patient encounters were sampled, out of which 193 physicians provided data on 618 (73%) of the encounters sampled. The results of analyses of the effect of patient race and SES on physician perceptions of and attitude towards patients, controlling for patient age, sex, race, frailty/sickness, depression, mastery, social assertiveness and physician characteristics, are presented. These results supported the hypothesis that physicians' perceptions of patients were influenced by patients' socio-demographic characteristics. Physicians tended to perceive African-Americans and members of low and middle SES groups more negatively on a number of dimensions than they did Whites and upper SES patients. Patient race was associated with physicians' assessment of patient intelligence, feelings of affiliation toward the patient, and beliefs about patient's likelihood of risk behavior and adherence with medical advice; patient SES was associated with physicians' perceptions of patients' personality, abilities, behavioral tendencies and role demands. Implications are discussed in terms of further studies and potential interventions.