The cerebral cortex taken post mortem from a case of Alzheimer's disease was examined especially with regard to the relation between blood vessels and senile plaques. Many senile plaques had central cores, composed of such matter as degenerated blood vessels and basement membranes with abundant amyloid fibrils. The components of senile plaques seemed to be degenerated neuronal and glial tissue compressed by developed basement membranes and amyloid fibrils. From this we would like to emphasize that senile plaques seem to be caused by amyloid fibrils and degenerated capillaries.