Forty-three patients with computed tomographic scan findings of decreased attenuation in the periventricular white matter (PVWM) region were studied. Clinical evaluation revealed presence of hypertension in 36 patients (84%) and cerebrovascular risk factors in 41 patients (95%). Unilateral or bilateral neurological deficits were present in 40 patients (93%). Neuropsychological evaluation in 27 of them revealed features of subcortical dementia. Magnetic resonance imaging in seven cases demonstrated high-intensity areas in the deep white matter region on T2-weighted imaging. Pathological evaluation in four patients revealed demyelination without inflammatory cells and infarctions in the PVWM region, lacunar infarctions in the basal ganglia and brain stem, and marked arteriosclerosis. The study indicated that most (95% in this series) of the patients with computed tomographic scan findings of decreased attenuation in the PVWM region had cerebrovascular risk factors and various neurological and neuropsychological features of subcortical dementia. Pathologically, these lesions represented areas of infarction and demyelination, along with diffuse arteriosclerosis.