The cellular distribution of nicotinic acetylcholine receptors was studied in the frontal cortex (area 10) of 1) Alzheimer patients and compared to 2) age-matched and 3) middle-aged controls using the monoclonal antibody WF 6 and an immunoperoxidase protocol. Statistical analysis revealed significant differences between the number of labeled neurons among all three groups tested (middle-aged controls greater than aged controls greater than Alzheimer cases). No differences were seen for cresyl violet-stained samples. These findings underline that the nicotinic receptor decrease found with radioligand binding may reflect a postsynaptic in addition to a presynaptic component.