1. Haemodynamic and renin responses to dynamic exercise before and after intravenous β-adrenoreceptor blockade with propranolol were compared in twenty-one patients with essential hypertension and either high (n = 7), normal (n = 7) or low plasma renin activity (n = 7).
2. Renin and heart-rate responses to exercise and β-receptor blockade diminished from high-renin to normal and to low-renin patients, effects which were blunted with increasing age.
3. Among the renin groups cardiac output, stroke volume, diastolic pulmonary artery pressure, systemic pressure and peripheral vascular resistance as well as their changes produced by exercise and acute β-receptor blockade were not significantly different.
4. Long-term anti-hypertensive propranolol effects correlated with the pre-treatment renin status, renin stimulation and its suppression by acute β-receptor blockade as well as with the exercise tachycardia and the patient's age.
5. The results suggest different adrenergic control mechanisms in renin sub-types of essential hypertension, age being a modulating factor.