AbstractNumbers of serotonin (5‐HT) recognition sites of total 5‐HT1, 5‐HT1Aand 5‐HT2subtypes have been measured in frontal, temporal and parietal cortex from human brain postmortem, using binding of [3H] 5‐hydroxytryptamine (5‐HT), [3H] 8‐hydroxy‐2‐(di‐n‐propylamino) tetralin and [3H] ketanserin, respectively. A comparison has been made between 11 patients with Alzheimer's disease (AD) and 20 matched controls. Significant disease‐related differences were observed only in the parietal cortex for total 5‐HT1and 5‐HT2recognition sites. Age‐related decrease in numbers of 5‐HT2recognition sites was seen in the controls, whereas an age‐related increase in the numbers of the same site was seen in AD patients. These changes are discussed in relation to disease severity and cortical