Components of the renin-angiotensin system (RAS) are expressed in a number of areas in the brain involved in cardiovascular control. However, it has been difficult to link RAS actions in circumscribed brain regions to specific physiological functions. In a study appearing in this issue of the JCI, Sakai and associates use a combination of sophisticated transgenic techniques and stereotaxic microinjection of recombinant viral vectors to demonstrate a pivotal role in the regulation of thirst and salt appetite of angiotensin II generated in the subfornical organ in the brain (see the related article beginning on page 1088).