AUTOPSY sections of the temporal and parahippocampal gyri were incubated with the monoclonal antibody M35 to label muscarinic acetylcholine receptors. Senile plaques were visualized either by counterstaining with Congo red or by Bielschowsky silver-stain of adjacent sections. The antibody labelled pyramidal and non-pyramidal cells in the grey matter, as well as fibrous astrocytes in the white matter and first cortical layer, of elderly control brains. In AD brains however, the grey matter was characterized by prominently labelled fibrous astrocytes and few or poorly labelled neurones. M35-immunoreactive astrocytes were often associated with senile plaques. These findings suggest that plaque-associated astrocytes may be responsive to acetylcholine or cholinergic drugs.