Angiotensin II acts on the brain to produce a variety of effects including elevation of arterial blood pressure, increased release of vasopressin and ACTH, stimulation of drinking and sodium appetite, and natriuresis. Many, and possibly all, of these effects can be produced by centrally administered angiotensin II or by circulating angiotensin II, which appear to act at common receptor sites located in the circumventricular organs. Whether these effects are normally produced by blood-borne angiotensin II formed by the renal renin-angiotensin system, by angiotensin II formed centrally by the putative brain renin-angiotensin system, or by both, remains to be determined. A large body of information concerning the site and mechanism of these different central actions of angiotensin II is available, and the physiologic significance of these actions is beginning to be understood. Nevertheless, much additional research will be required before the actions of angiotensin II on the brain are completely understood.