In healthy volunteers, the azapirones--buspirone, ipsapirone, and gepirone--increase plasma cortisol and decrease body temperature; buspirone and gepirone also increase plasma prolactin and growth hormone. Data from animal studies suggest that the ability of azapirones to decrease body temperature and increase corticotropin and corticosterone is mediated by stimulation of presynaptic and postsynaptic serotonin (5-hydroxytryptamine, 5-HT) type 1A subtype receptors, respectively. The mechanism of altered growth hormone and prolactin secretion is less clear. While animal studies implicate changes in dopamine function, current human investigations suggest that 5-HT1A receptors also may be involved in these endocrine responses. Further investigations, using more selective 5-HT receptor antagonists, will be required to resolve this issue.