Weekly infusion with arginine vasopressin (AVP) (2 micrograms.kg-1.day-1) exerted a slight stimulatory effect on the adrenal growth of intact female rats and induced a 2-fold rise in plasma aldosterone concentration (PAC), without apparently affecting corticosterone (B) and ACTH secretions. Weekly dexamethasone (Dx) administration (125 micrograms.kg-1.day-1) caused a marked adrenal atrophy, a conspicuous suppression of B and ACTH productions, and a 5-fold increase in PAC. AVP infusion reversed the Dx-induced adrenal atrophy. It did not counteract the suppression of B and ACTH secretions, nor did it change PAC. These findings suggest that chronic AVP treatment is able to stimulate adrenal growth by a Dx-insensitive mechanism (i.e. independent of any change in ACTH secretion). Conversely, AVP may enhance the steroid secretory capacity only in adrenocortical cells in which the maintenance of the steroidogenic machinery is assured by normal levels of circulating ACTH.