This group investigated 62 caucasian subjects with essential hypertension, and measured renin levels on low and high sodium intake for two weeks each. They also studied the adrenal (aldosterone concentration) and renal haemodynamic (renal plasma flow) response to an infusion of angiotensin II. After excluding the subjects with low renin concentrations on a low sodium intake, they divided those with normal and high renin levels into modulators and non-modulators according to high or low responsiveness to angiotensin II. They showed that, even though all three groups had similar levels of systolic, diastolic and pulse pressure, the non-modulator and low renin subjects were similarly sodium sensitive in terms of blood pressure response to high salt, this being in both groups around three times that of the modulators.