1. 20 subjects with uncomplicated essential hypertension were studied, 10 of whom were on propranolol treatment. Several blood samples for determination of total and active renin were drawn simultaneously from the renal artery and vein after angiographic studies.
2. In all patients renal blood flow was measured by Hippuran-clearance at the time of blood sampling. Intrarenal blood flow was assessed by xenon-washout.
3. The results indicate that under basal conditions renin is secreted mainly in the active form, although secretion of inactive renin does occur. During propranolol treatment there is a tendency for secretion of active renin to be reduced.