Serotonin 2A receptors (5-HT2A), and serotonin reuptake transporters (5-HTU) are involved in regulating some autonomic and cognitive processes. While the pre-synaptic and post-synaptic distribution of 5-HT2A receptors is unknown in the primate hypothalamus, in cortex, the majority of 5-HT2A receptors are located post-synaptically on pyramidal and glial cells. The density of 5-HT2A and 5-HTU sites declines with age in the primate and rodent hippocampus and frontal lobe but such changes have not been documented in the hypothalamus. To assess age-related changes in the density of 5-HT2A and 5-HTU binding sites in the rhesus monkey (Macaca mulatta) hypothalamus, autoradiographic ligand binding was utilized within the anterior, tuberal, and posterior hypothalamus, and the mammillary body (MMB) of 11-17 monkeys (4.4-31.8 yo). 5-HTU binding was assayed with tritiated citalopram and 5-HT2A with iodinated dimethoxyaminopropane (DOI). The density of 5-HTU binding was significantly reduced with age in the anterior (R= -0.57, N= 16, P=0.021), tuberal (R= -0.627, N= 17, P= 0.007), and posterior (R= -0.053, N= 15, P= 0.042) hypothalamus. Conversely, only the MMB displayed a significantly lower 5-HT2A density in aged animals (R=- 0.631, N= 11, P= 0.037). These results show a significant age-related decline in CIT binding throughout the hypothalamus, suggesting an age-related reduction in its serotonergic innervation. While we were unable to evaluate 5-HT U binding in the MMB, our results show a significant decline in DOI binding in this nucleus. Future studies are needed to determine the 5-HT2A receptor distribution in the monkey hypothalamus. (Supported by NIH Grant-P01-AG00001-29 and RR-00165).