As part of a prospective clinicopathologic study, a cohort of 105 "normal" elderly volunteers was investigated with computed tomographic scans, psychometric testing (Extended Scale for Dementia [ESD]) and neurologic examination. Computed tomographic scans were evaluated for the presence or absence of white matter lucencies, termed leuko-araiosis. These are defined as patchy or diffuse areas of decreased attenuation involving only white matter and with no change in adjacent ventricles or sulci. The nine controls with leuko-araiosis had lower scores on the ESD than the 96 controls without leuko-araiosis (mean ESD with leuko-araiosis, 227.1 +/- 14; without leuko-araiosis, 237.1 +/- 8), and the difference remains significant even after adjusting for the possible confounding effects of age, sex, education, and infarct detected on computed tomography. Significant differences were also found comparing subjects with leuko-araiosis and those without in respect to abnormal gait, limb power, plantar response, and the rooting and palmomental reflexes. Leuko-araiosis may represent a marker for early dementia. The pathophysiology of this finding remains uncertain. Our results suggest that white matter abnormalities play a role in the development of intellectual impairment in the elderly.