1. Plasma renin activity, response to saralasin and exchangeable sodium have been measured in 43 patients with early renal disease.
2. Blood pressure was directly proportional to plasma renin activity. However, mean plasma renin activity was lower in patients with renal disease than in normal controls.
3. Blood pressure fell in response to saralasin infusion in proportion to the pre-infusion plasma renin activity.
4. Exchangeable sodium in hypertensive patients with renal disease did not exceed that in normotensive patients in contrast to earlier reports. Discrepancies may arise from the difficulty in interpreting measured exchangeable sodium in relation to body build.