1. Factors associated with advanced cerebrovascular damage incidentally seen on brain magnetic resonance imaging (MRI) were investigated in a population of 34 normotensive and 54 hypertensive asymptomatic elderly individuals (69 +/- 5 years). 2. Four or more 'lacunar' lesions per subject were considered to be advanced changes, based on the distribution in normotensive subjects and were found in 11 (20%) out of 54 hypertensive subjects. 3. Compared with the remaining 43 hypertensive patients with fewer or no lacunae, the proportion of subjects over 70 years of age who had electrocardiographic (ECG) evidence of left ventricular hypertrophy (LVH) was significantly higher in this group of hypertensive patients. Patients with multi-lacunar lesions also showed significantly higher 'office' and average ambulatory, in particular, blood pressure during sleep and less nocturnal blood pressure fall, than those with fewer or no lacunae. Furthermore, they showed a higher predicted whole blood viscosity and a lower high density lipoprotein (HDL)-cholesterol. The predictive values of LVH on ECG for the presence of multi-lacunar lesions in hypertensive patients were substantially high (70-90%). 4. The data suggest that silent advanced cerebrovascular damages on MRI are not rare among asymptomatic elderly hypertensive patients and are associated with various cerebrovascular risk factors. A useful marker for their identification appears to be ECG-LVH.