BACKGROUND: Overstimation of blood pressure(BP) by clinic measurements occur in about 20 to 30% of subjects(white-coat hypertension) who may, consequently, be misdiagnosed as hypertensives and received unnecessary medications. The clinical significance of white-coat hypertension and its effects on the cardiovascular wystem have not been studied systematically.This study was designed to evaluate the influences of white-coat hypertension and white-coat effect, defined as difference between clinic and ambulatory BP, on the LV mass and diastolic function. METHODS: LV mass index was calculated and LV systolic and diastolic function were assessed by the analysis of mitral and pulmonary venous flow velocity in 45 untreated essential hypertensives and 20 normotensives(NT). Ambulatory BP monitoring classified hypertensives as white-coat hypertensives(WCHT,n=20) and sustained hypertensives(SHT, n=25). RESULTS: 1) Left ventricular systolic indices were not different among the three groups. 2) Left ventricular mass inedx of WCHT(114.5+/-36.3g/m2) was similar to that of SHT(115.6+/-34.9g/m2) and was significantly greater than that of NT(86.5+/-37.7g/m2)(p<0.05). 3) Some of left ventricular diastolic parameters(isovolumic relaxation time, E/A ratio, A velocity, pulmonary systolic fraction, ratio of systolic to diastolic forward flow velocity) of WCHT and SHT were significantly different from those of NT(p<0.05), but there were no differences between two hypertensive groups. 4) Even though both systolic and diastolic white-coat effect in WCHT were significantly greater than those of SHT(o<0.05),white-coat effect did not influence on the left ventricular mass or function in both groups. CONCLUSION: An increased left ventricular mass and diastolic dysfunction in WCHT suggests that white-coat hypertension could not be considered as an entirely innocuous clinical condition.