Angiotensin II receptor subtypes have been localized in brain by using a novel nonpeptide AII-type 1 receptor antagonist to compete with [125I]AII binding in an autoradiographic study. These data contrast with results obtained using the AII-type 2 antagonist PD123177. Both receptor subtypes appear to exist in the brain, but the type 1 receptor predominates in the small regions of brain where AII binding is highly concentrated. DUP 753 may have a central action involved in its unique antihypertensive effect.