Autoantibodies against glial fibrillary acidic protein (GFAP) were investigated by ELISA test in sera of patients suffering from senile dementias and in healthy aging people. One hundred eight subjects divided into control, vascular dementia (VD), presenile Alzheimer's disease (AD), and senile Alzheimer's disease (SDAT) groups were included in the study. VD patients showed the highest antibody titers when compared to controls, whereas AD had the lowest titers when compared to the other groups. These results do not support the utility of anti-GFAP antibodies as useful markers of Alzheimer's disease, suggesting that their presence is a secondary phenomenon to blood-brain barrier disruption.