1. Injections of antagonists of angiotensin II into the cerebral ventricles of normotensive and spontaneously hypertensive rats were performed in order to assess the role of the isorenin-angiotensin system in the brain. 2. No hypotensive effect was obtained in either normotensive or hypertensive rats, suggesting that intracranial isoangiotensin has little role in the pathogenesis of spontaneous hypertension in the rat.