Image analysis apparatus was used to count and measure glial and neuronal perikarya in ten size classes in the midfrontal region and superior temporal gyrus of 18 patients with senile dementia of the Alzheimer type for comparison with 12 age-matched normal specimens. Brain weight was about 8% less in the dementia group. The major differences had to do with larger neurons, which in dementia were reduced by about 40% in the frontal cortex and 46% in the temporal region. The concentration of neuritic plaques did not correlate significantly with brain weight, cortical thickness, or cell counts.