The distribution of serotonin (5-HT) receptor subtypes was measured by ligand binding to sections of the temporal cortex of brains from controls and patients with Alzheimers-type dementia (ATD). ATD was associated with a reduction in total 5-HT-2 receptors in cortex, with no significant change in 5-HT-1 receptors. Autoradiography was used to measure the distribution of 5-HT receptors within the temporal cortex. Three bands of high density of 5-HT-2 receptors were present in control cortex, and markedly reduced in ATD cortex. In addition a reduction of binding to 5-HT-1A receptors was also apparent from the autoradiographs. The relationship between these 5-HT receptor changes and other neurochemical deficits in ATD are discussed.