Silent cerebrovascular disease in the elderly. Correlation with ambulatory pressure. Does the average daily blood pressure correlate with hypertensive cerebrovascular disease better than the casual pressure, as has been reported in other target organ involvement? We investigated the associations of two abnormal findings on brain magnetic resonance imaging suggestive of a vascular etiology, low intense foci (lacunae), and periventricular hyperintense lesions on T1- and T2-weighted images, with both office and average daily blood pressure values in a population of 73 healthy normotensive and hypertensive elderly individuals (70 +/- 6 years old). Lacunae were detected in 34 subjects (47%); the number per subject ranged from 0 to 19 and was significantly correlated with advancing age. Furthermore, these changes were supposedly related to the average of noninvasive ambulatory (24-hour and during awake and asleep periods) pressure recordings but not to office pressures. The grade of periventricular hyperintensity was also significantly associated with advancing age and the average of ambulatory systolic pressure recordings, particularly during sleep, but not with office blood pressure. In comparisons of normotensive, "office hypertensive," and hypertensive subgroups, abnormalities on magnetic resonance imaging were appropriate to the level of the 24-hour blood pressure measurements but not to that of clinic pressure. In hypertensive patients, the presence of electrocardiographic evidence of left ventricular hypertrophy was also associated with greater abnormalities on magnetic resonance imaging. We conclude that ambulatory blood pressure monitoring is superior to casual pressure measurements in predicting latent cerebrovascular disease, which is unexpectedly common in apparently healthy elderly subjects. 