Acute infusions of angiotensin II or rat renin into intact rats did not stimulate aldosterone secretion. Hypophysectomy plus nephrectomy lowered the basal secretion of aldosterone. Acute infusions of angiotensin into these rats stimulated aldosterone secretion to the levels of intact control rats. Intact rats on a sodium-deficient diet for 10 days had markedly elevated aldosterone secretion rates in vivo and in vitro and increased width of the zona glomerulosa. Continuous infusions of angiotensin for 7–12 days did not produce any of these changes. These data suggest that the increased aldosterone secretion rate in sodiumdeficient rats may not be regulated by the renin-angiotensin system. (Endocrinology76: 657, 1965).