In anaesthetized cats, atenolol (3 mg X kg-1 i.v.) produced an immediate reduction in blood pressure, heart rate and aortic nerve discharge. However, 30 min and 60 min after atenolol there was a shift to the left of the curve relating aortic nerve discharge to mean arterial blood pressure indicating a delayed resetting of the baroreceptors. There was no evidence that atenolol altered the sensitivity of the baroreceptors.