To evaluate the morphological and functional characteristics of the heart in elderly patients with white coat hypertension, we performed an echocardiographic study in 67 elderly individuals older than 60 years: 17 patients with white coat hypertension, 34 patients with true hypertension, and 16 normotensive control subjects. White coat hypertension was defined as a mean 24-hour ambulatory systolic blood pressure of less than 140 mm Hg associated with office hypertension. Cardiac responses to an isometric handgrip exercise test were used to evaluate left ventricular functional reserve. Left atrial dimension and left ventricular mass index were significantly greater in the white coat hypertension group than in the normotension group (P<.05) but were similar to values in the true hypertension group. Left ventricular diastolic function, expressed by peak late-early filling ratio of diastolic mitral flow, showed increasing impairment in the order of the normotension, white coat hypertension, and true hypertension groups (analysis of variance, P<.05); the ratio in the white coat hypertension group tended to be higher than that in the normotension group (unpaired t test, P=.054). The relation between fractional shortening and end-systolic stress did not shift downward after handgrip exercise in the white coat hypertension group, indicating that functional reserve in the left ventricle was maintained. Thus, patients with white coat hypertension had a moderately increased left atrial dimension and left ventricular mass in association with a tendency for disturbed diastolic function, although systolic functional reserve remained the same. These findings suggest that white coat hypertension in the elderly may not be innocent.