In the neuropathological investigations of 32 demented patients with severe cerebral amyloid angiopathy (CAA), we found an unusual case, a 90-year-old woman, presenting with the pathology of atypical Alzheimer's disease (AD). The case showed severe plaque-like angiopathy, in which all the senile plaques except for some diffuse plaques were formed around amyloid beta (/A4) protein-laden vessels. Analysis of the amyloid beta protein precursor gene from the patient revealed no mutation. Our results have indicated that, among demented patients with severe CAA, there is the vascular variant of AD characterized by severe plaque-like beta protein angiopathy.