BACKGROUND: Blood pressures rneasured by a nurse at reception room as a part of routine physical examination are oft,en used as a indicator of medical care. Blood pressure at reception room and consultation room are, however, often different to each other and these differences are caused by various factors including difference of white coat effect by nurse and doctor. Thus, this study was performed in order to know whether blood pressure difference really exit, and its associated factors. METHODS: Two hundred ninety one patients who visited to one university hospital farnily practice were enrolled in this study. Blood pressure and pulse rate at reception room and consultation room, waiting t,ime, time interval between reception and consultation, smoking status, and intake of coffee and food were collected. Nine patients were excluded, because blood pressure either at reception room or at consulation room was not recorded. This study was performed by one nurse and two doctors. They defined the guideline for method of blood pressure measurement before the study, and used the same kind of indirect cuff sphygmomanometer. RESULTS: Two hundred eighty two patients were analyzed. The number of men was one hundred twenty five. Systolic blood pressure at consultation room was higher than that at reception room by 1.6+/-11.9mmHg (P<0.05). Sixty five cases(65%) in systolic blood pressure and 111 cases(40%) in diastolic blood pressure showed blood pressure differences more than 5mmHg. The group with systolic blood pressure difference between reception room and consultation room(SBP) in more than 5mmHg is more likely to be hypertensive than the group with SBP in less than 5mmHg(P<0.01). More female patients(66%) and hypertensive patients(59%) were belong to the group whose systolic blood pressure at consultation room were 5mmHg higher than at reception room(P<0.01). Twenty four patients(30%) of the group whose systolic blood pressure at reception room were 5mmHg higher than at consultation room had cigarette smoking within 1 hour, and this ratio was significantly higher than the other groups whose systolic blood pressure difference was less than 5rnmHg or systolic blood pressure at consultation room were 5mmHg higher than at reception room(P<0.01). There was relatively good concordance in classifying hypertension and normal blood pressure according to measurement site(Overall kappa, 0.747, P<0.01). CONCLUSIONS: Many patients showed blood pressure differences more than 5mmHg between reception room and consultation room. Systolic blood pressure at consultation room was higher than that at reception room, and there was relatively good concordance in classifying hypertension and normal blood pressure according to measurement site, but the adverse effect by misclassification should not be neglected. The importance as well as the limitation of blood pressure measurement at reception room should be considered in screening and treating hypertensive patient. Every time when blood pressure is taken, physicians should keep in mind to consider patients factors which may influence blood pressure level.