• A quantitative and clinically correlated investigation was carried out to determine the divisional distribution of volumetric and cell-packing density changes in the amygdala in patients with advanced aging and senile dementia. Normal controls show relatively little, but nevertheless significant, age-related change. In contrast, the amygdala undergoes very marked degeneration in patients with senile dementia, which preferentially affects the morphologically, developmentally, and connectionally older medial, medial central, and cortical nuclei. These findings strengthen the possibility that the amygdala participates in the behavioral changes that occur in senile dementia.