We studied neuropathological changes of the amygdala in 10 cases of presenile Alzheimer's disease. According to the anatomical classification of the amygdala, we subdivided the corticomedial group into 3 parts, and the basolateral group into 8 parts. We investigated qualitatively neuronal loss, and quantitatively the numbers of neurofibrillary tangles (NFTs) and senile plaques (SPs) in 11 parts. The degree of atrophy of the amygdala was also checked in relation to the clinical stages of the disease. Neuronal loss was more prominent in the later clinical stages. It was more intense in the corticomedial group than in the basolateral group. The density of NFTs tended also to be greater in the corticomedial group than in the basolateral group, although it did not always increase in parallel with the progress of dementia. The density of SPs was greater in the basolateral group than in the corticomedial group, and tended to increase in parallel with the progress of the disease. Atrophy of the amygdala was generally more prominent in the more advanced clinical stage. The distribution pattern of neuronal loss was similar to that of NFTs in the amygdala, whereas the distribution pattern of SPs was quite different.