Braak's argyrophilic grains (BAG) are spindle-shaped structures originally described in patients with dementia. We have determined that the prevalence of BAGs in an unselected series of 300 consecutive autopsies of subjects over the age of 30 is 5.6%, or 11.7% if only subjects older than 65 are considered. All the 17 subjects identified were older than 68; 6 received other neuropathological diagnoses of degenerative disease and 11 did not. Only 2 of the latter had shown clinical evidence of mental impairment. Braak's argyrophilic grains were associated with ballooned neurons, superficial linear spongiosis, and gliosis of entorhinal cortex and amygdala. Subcortical neurofibrillary tangles were consistently found in patients with dementia, but not in other subjects. In a separate series studying the prevalence of BAG in neurodegenerative diseases, we found a strong, but not universal association with progressive supranuclear palsy, and to a lesser degree with the lobar atrophies (Pick's disease and corticobasal ganglionic degeneration). Numerous BAG were present in occasional cases of diffuse Lewy body disease, multiple systems atrophy, and motor neuron disease. We conclude that rather than defining a single disease, BAG constitute lesions that accompany several degenerative diseases, but also occur in normal elderly subjects, and rarely in demented subjects without other major histological findings.