Experiments were performed in urethane-anaesthetized rabbits using ventriculo-cisternol perfusion. Central infusion of angiotensin II (50 ng/kg/min) induced a rise in blood pressure which was accompanied by an increase in the noradrenaline concentration of the cerebrospinal fluid. Both effects were highly correlated. Conversely, an i.v. infusion of noradrenaline (5 micrograms/kg/min) which caused a similar increase in arterial pressure did not affect the cerebrospinal fluid catecholamine levels. These results suggest that peripheral cardiovascular effects of centrally administered angiotensin II are related to the activation of noradrenaline structures in the brain.