Amygdalae of patients with Alzheimer's disease (AD), Parkinson's disease, Down's syndrome, diffuse Lewy body disease or a combination of these diseases were probed with antibodies to neurofilament proteins as well as with Lewy body (LB)- and paired helical filament-specific antibodies. The results indicate that the amygdala is severely affected by the accumulation of both neurofibrillary tangles (NFTs) and LBs in most cases of the diseases mentioned above, and that amygdala LBs have a similar epitope composition to that of LBs in the brain stem and cerebral cortex. While large numbers of both LBs and NFTs were seen in different neurons within the amygdala, these two lesions frequently occurred together in the same neurons of the amygdala. These findings are in contrast to other sites that accumulate LBs and NFTs, but rarely both lesions in the same neuron. Thus, amygdala neurons may be selectively vulnerable to developing both LBs and NFTs, and these inclusions may play a role in the massive degeneration of these neurons in AD and LB disorders of the elderly.