The sites that initiate angiotensin effects on vascular and extravascular tissues have historically been identified as "the angiotensin II (Ang II) receptor." However, this unitary perspective of a single receptor responding to a single hormone has been revised with the molecular cloning of angiotensin-responsive receptors. The mammalian proto-oncogene MAS has been identified as a novel neuronal angiotensin receptor, which responds preferentially to Ang III, and has other unusual pharmacological properties. Although its tissue distribution suggests it may function normally in the brain in sites not normally associated with angiotensins, it shares many structural and functional features with the cloned vascular Ang II receptor. The understanding of the MAS/angiotensin receptor may compel a basic rethinking of many aspects of the cardiovascular biology of the renin-angiotensin system.