Most of the 52 patients on maintenance dialysis investigated in this study suffered from arterial hypertension in spite of efforts to reduce ‘dry weight’. In this situation we found that the majority of patients were underweight and that total body water, extracellular volume and blood volume were close to normal when related to reference systems consisting of height and age. Hypertensive patients were not volume expanded as compared to normotensive patients and controls. Plasma renin activity and angiotensin II were elevated in a few patients, with a trend to higher levels in the more hypertensive patients. Various approaches attempting to correlate blood pressure and the respective volume-renin factors did not prove to be conclusive in explaining the maintenance of hypertension in chronic renal failure on the basis of the sodium-renin feedback.