The relation between carotid blood flow measured by Doppler spectrum analysis and brain atrophy on computed tomography (CT) was studied in 22 subjects with multiple lacunar cerebral infarctions. The subjects were divided into two groups, 7 patients with multi-infarct dementia (MID) (mean age 73 years) and 15 nondemented lacunar stroke subjects (NDLS) (mean age 66 years), according to DSM III criteria. All subjects had a score of 7 points or more on Hachinski’s ischemic score and showed no carotid artery stenosis. Systolic peak frequency of the common carotid artery (CCA) was measured by Doppler spectrum analysis (Angioscan II). Brain atrophy was measured quantitatively on CT images by two-dimensional measurement using a digitizer. Peak frequencies were lower in MID than in NDLS. Brain atrophy was more severe in MID than in NDLS. There was a significant correlation between peak frequencies and brain atrophy in all subjects. These results indicate that CCA blood flow may reflect brain function in patients with multiple lacunar infarction