Using magnetic resonance imaging and digitized brain computed tomography, we evaluated 33 elderly patients with documented lacunar stroke and divided them into three groups (nondemented, « = 15; borderline, ra=9; and demented, n=9) by neuropsychological assessments and DSM III criteria. We evaluated the extent of white matter lesions and the degree of atrophy of specific anatomic structures, such as the corpus callosum, using magnetic resonance imaging and quantified the volumes of the ventricles, the subarachnoid spaces, and the brain parenchyma using digitized brain computed tomography. Our results show that both borderline and demented patients had significantly more extensive white matter lesions than nondemented patients, indicating a significant relation between the extent of white matter lesions and intellectual decline. In addition, borderline and demented patients had significantly larger ventricles and more brain atrophy than nondemented patients; demented patients also had significantly larger subarachnoid spaces than nondemented patients and more brain atrophy than borderline patients. Our findings suggest that in most patients with lacunar stroke, periventricular and subcortical white matter lesions with subsequent white matter atrophy first induce ventricular enlargement, followed by generalized brain atrophy, resulting in dementia. (Stroke 1989;20:1488-1493 V ascular dementia and dementia of the Alzheimer type are two main types of dementia. Vascular dementia can be divided into three major subgroups: multiple discrete strokes following thrombotic or embolic occlusion of large cerebral arteries (multi-infarct dementia) 1 -2