Infusion of synthetic ovine CRF (10 or 100 micrograms/h) into the lateral lateral cerebral ventricle for 24 h increased mean arterial blood pressure of conscious sheep. CRF infusion also increased urine output and sodium excretion. Intravenous infusion of CRF (100 micrograms/h) or intraventricular infusion of artificial CSF had no effect on blood pressure. Intraventricular infusion of ACTH (1-24) at 0.5 micrograms/kg per day, a rate of infusion which has no systemic effect on blood pressure, also raised mean arterial pressure. These studies suggest that two peptides involved in the physiological response to 'stress' may influence blood pressure by mechanisms which do not involve stimulation of adrenocortical steroid production.