Buspirone hydrochloride, a compound with novel chemical structure, has been reported to be anxiolytic in man. Its mechanism of action as an anxiolytic is unknown, but preclinical studies have shown that it produces effects consistent with both a dopamine agonist and antagonist. In man, buspirone hydrochloride at doses of 30, 60, and 90 mg orally significantly elevated plasma prolactin (PRL) and growth hormone (GH) concentrations. The apparent increase in PRL secretion was dose dependent, but that of GH was not. The increase in PRL secretion could be due to a dopamine antagonist effect at the pituitary gland. A dopamine agonist action at hypothalamic dopamine receptors could account for the increase in GH secretion. Benzodiazepine anxiolytic drugs also increase serum GH levels in man, by a mechanism that has not been clearly established. It may be that buspirone and benzodiazepine drugs stimulate GH secretion by a common mechanism that is related to their anxiolytic actions.