Expression of chromogranin A in various neurological diseases was examined immunohistochemically using purified anti-human chromogranin A antiserum. The antibody stained dystrophic neurites in senile plaques in Alzheimer disease brain, Pick bodies and ballooned neurons in Pick's disease brain, some Lewy bodies in the substantia nigra of Parkinson's disease, and axonal swellings in various neurological conditions including Parkinson's disease, striatonigral degeneration, Shy-Drager syndrome, amyotrophic lateral sclerosis and cerebral infarction. The present study shows that expression of chromogranin A is not an exclusive feature of Alzheimer disease or Pick's disease, and indicates that it could be a useful marker for various neurological diseases.