1. Plasma renin concentration, intra-arterial pressure, cardiac output and total peripheral resistance have been studied in 50 patients with essential hypertension and normal renal function.
2. Total peripheral resistance and plasma renin were negatively correlated (r = −0·45), indicating that ‘high-renin’ essential hypertension is not necessarily associated with arteriolar vasoconstriction.
3. The inverse relation between mean arterial pressure and plasma renin (r = −0·46) suggests a role for the renal baroreceptor mechanism in the suppression of renin in ‘low-renin’ hypertension.
4. Cardiac output was positively related to plasma renin concentration (r = +0·42).
5. Multiple regression analysis indicates that the described relationships were independent of age.