The circulating levels of aldosterone (A), cortisol (F), prolactin, ACTH and potassium and the PRA were studied in 8 (6 males and 2 females) healthy normotensive subjects after 5-hydroxy-tryptophan (5OHT), or pizotifen (Piz) or placebo oral administration. In the same subjects 5OHT was administered twice: after placebo and after dexamethasone pretreatment. The results showed a significant increase of A, ACTH and F after 5OHT plus placebo administration without any change of PRA, potassium or prolactin levels; dexamethasone pretreatment suppressed ACTH and F but was uneffective on the response of A to 5OHT. Only A levels showed a significant decrease after Piz administration, the other studied parameters were unaffected by the blockade of the 5HT2 receptors by Piz. The administration of placebo induced a slight but not significant decrease of the studied parameters. Our results suggest the existence of a physiologic serotonergic control of A secretion, a pituitary factor could be one of the putative links between the central serotonergic activation and the adrenal secretory response.