Although establishing that a patient is suffering from dementia of the Alzheimer type initially reflects a clinician's opinion, neuropathological study is for the present the most definitive examination to confirm the clinical diagnosis of Alzheimer disease. We review several comprehensive publications attempting on a quantitative basis to differentiate the changes occurring with normal aging of the human brain from those indicative of Alzheimer disease. New morphometric data on 5 histopathological lesions in the mesial temporal cortex of 42 subjects indicate that, when multivariate analyses are performed on such microscopic information, a diagnostic prediction about the brain of any unknown individual should indeed be possible with a statistically calculated degree of certainty