To clarify (1) the localization of flotillins in human brain tissue acid (2) the relationship between senile plaque formation and flotillins localization, we performed Western blotting and immunohistochemical analysis. Flotillins 1 and 2 were shown as 48 and 42 kDa bands, respectively, in human brain. The cerebral cortex showed a broad band-like labeling in entire layers. Flotillins were abundant in pyramidal neurons and astrocytes in the white matter. The intensity of the bandlike labeling throughout the cortex became stronger with the development of senile plaque formation, and strongest in Alzheimer's disease. These findings suggest that flotillins are associated with progression of Alzheimer pathology. (C) 2000 Published by Elsevier Science Ireland Ltd.