1. The relationships between blood pressure and the components of the renin-angiotensin-aldosterone system were studied in 49-year-old men (n = 120) who were selected at random from the total population so as to be representative of all blood pressure levels.
2. Only plasma aldosterone concentration was significantly correlated with blood pressure, both in the whole study group (r = 0.22; P < 0.02) and in the hypertensive blood pressure range (r = 0.36; P < 0.02). The hypertensive subjects had a significantly higher plasma aldosterone concentration than the borderline and normotensive subjects.
3. Multiple regression analysis including factors related to the renin—angiotensin—aldosterone system, showed that the 24 h urinary excretion of noradrenaline was the factor most strongly correlated to. plasma aldosterone.
4. The findings indicate that aldosterone may be the most important component of the renin—angiotensin—aldosterone system in the development and maintenance of essential hypertension.