Angiotensin ll binding sites were localized and quantified in individual brain nuclci frorn single rats by incubation of ussue sections with I nM ra¡.lSarrl-angiotcnsin II. frHl-Ultrofilm autoradiography. computerized microdensitometry and comparison with rr¡-standards. High angiotensin II binding was present in the circumvcntricular organs (organon vasculosum laminac tcrminal¡s. orga¡on subfornicalis and arca postrema). in sclccted hypolhalamie nuclei (nuclei suprachiasmatis pcrivcnlricularis and peRvcntricularis) and in rhe nuclcus tractus olfactorii lateralis, thc nucleus preopticus medianus. the dorsal molor nucleus ofthe yagus and the nucleus tractus solitarii. High aflinity (Ka from 0.1 to l.5x l0e M-r)angliolensin ll bindirg sites were demonitrated in the organon subfomrcalis, the nuclcus tractus solitarii and the area postrema after incubation of consecutivc sections from single ral brains with ¡r5l-fSartl-angiotcnsin II in concentrations from 100 pM to 5 nM. These results demonstate and chamcterize brain binding sites for angiotensin ll of variable high añinily binding both inside and outsidc the blood-brain barrier.