We studied immunocytochemically with 2 amyloid beta protein (ABP) antisera brains from 5 non-demented elderly subjects with evidence of diffuse periventricular white matter hypodensity on computed tomography. In periventricular white matter of all brains we found ABP reactive deposits arranged around small vessels walls. Furthermore ABP reactive deposits, identical to those currently called diffuse plaques, were detected in neocortex in amount proportional to that of white matter deposits. We suggest that ABP microangiopathy and parenchymal deposition is responsible of white matter rarefaction in a subset of cases with a diffuse hypodensity on CT scan which has been called leukoaraiosis.