To elucidate the role of leuko-araiosis observed on computed tomographic imaging among normal populations, 37 neurologically and cognitively normal volunteers ages 18 to 88 years were studied. Local cerebral blood flow was measured using stable xenon-enhanced computed tomography. Severity of leuko-araiosis and cerebral atrophy were graded on computed tomographic images. Leuko-araiosis was observed in 21.6% of normal volunteers, in 52.2% of patients with multi-infarct dementia (n = 23), and in 61.5% of patients with dementia of the Alzheimer type (n = 13). When multiple regression analysis was applied among normal volunteers, the degree of cerebral atrophy, advancing age, and local cerebral blood flow reductions of subcortical white matter correlated and contributed in that order of precedence to the presence and severity of leuko-araiosis. Combination of the unusual vascular anatomy of periventricular white matter together with cerebral hypoperfusion appears to be related to the occurrence of leuko-araiosis observed among neurologically and cognitively normal subjects. Further investigations should determine whether leuko-araiosis among this population is a risk factor for later cognitive impairments.