In sodium-depleted rats an intact pituitary was found to be essential for normal stimulation and maintenance of aldosterone production. To define better this pituitary involvement the effects on aldosterone production of whole and posterior pituitary extracts, ACTH, GH, FSH, LH and l-thyroxin injections were studied in hypophysectomized rats fed a diet low in sodium. None of the injections resulted in aldosterone secretion rates which approached those measured in intact, sodium-depleted rats. Whole pituitary extracts, ACTH and GH had some aldosterone stimulatory effect. In order to avoid the effects of prolonged hypophysectomy, rats were first sodium depleted and then hypophysectomized. The ability of pituitary hormones to maintain the elevated aldosterone secretion and in vitro production rate was studied. ACTH only partially maintained aldosterone secretion and in vitro production while maintaining corticosterone production in vitro. GH also partially maintained aldosterone secretion and production but had little or no effect on corticosterone production in vivo and in vitro. Treatment with ACTH plus GH or with whole rat pituitary glands completely maintained aldosterone production; ACTH plus GH maintained corticosterone production rates at normal or greater than normal levels. Rat pituitary glands had only a slight effect on corticosterone production. These results indicate that ACTH and GH are necessary for a normal response to sodium depletion, but do not rule out the possibility that other pituitary hormones are also necessary. (Endocrinology86: 728, 1970)