1. Anaesthetized, nephrectomized rats were infused intravenously with unlabelled angiotensin II (AII) or with [3H]angiotensin II (3H-labelled AII). The brain ventricular system was perfused with artificial cerebrospinal fluid. The perfusate was collected from the cisterna magna and analysed for AII by radioimmunological and biochemical methods.
2. No increase of immunoreactive AII in cerebrospinal fluid could be shown during intravenous infusion of AII.
3. During intravenous infusions of 3H-labelled AII at pressor doses small amounts of radioactivity were found in cerebrospinal fluid perfusate.
4. The radioactivity of cerebrospinal fluid outflow could not be related to AII.