Fibrous astrocytes were stained by the Sternberger (peroxidase-antiperoxidase) method, using paraffin sections of mid-frontal cerebral cortex of patients with senile dementia and of normals of similar age. The populations of fibrous astrocytes were similar in the molecular layer, but were widely divergent in layers II through VI. Here the mean count of fibrous astrocytes in senile dementia of the Alzheimer type was more than four times that of the normal aged cortex.