1. Prindolol and propranolol chronically cause a fall in mean blood pressure and mean plasma renin activity, but no correlation was observed between the two variables.
2. The response of blood pressure to prindolol and propranolol was not predicted by the basal plasma renin activity.
3. Propranolol administered acutely caused the plasma renin activity to fall with no acute change in blood pressure, whereas prindolol caused the blood pressure to fall with no change in plasma renin activity.
4. The effects of β-adrenergic-blocking drugs on plasma renin activity and blood pressure can be dissociated and it is unlikely that their hypotensive action is mediated through the renin-angiotensin system.
5. Basal plasma renin activity does not identify the patients who will respond to β-adrenergic-blocking drugs.