Intracerebroventricularly administered des-Asp-angiotensin I, when prevented from degradation by prior administration of captopril, attenuated dose-dependently the central pressor actions of angiotensin II and angiotensin III in the spontaneously hypertensive (SHR) and Wistar Kyoto (WKY) rats. This finding is the first demonstration of an intrinsic action of des-Asp-angiotensin I and, together with earlier finding of its increased production in the hypothalamus of the spontaneously hypertensive rat, may support the suggestion that the nonapeptide is a functional angiotensin that regulates the pressor action of angiotensin II and angiotensin III in the brain.