Influence of blockade converting enzyme on plasma renin activity (PRA), aldosterone and vasopressin secretion in 12 hemodialyzed patients with chronic renal failure and in 21 healthy subjects was observed. Our observation were provided during bed rest and water immersion tests. We didn't observe statistically significant influence PRA (increase after converting enzyme blockade) on vasopressin secretion in patients with chronic renal failure and in healthy subjects. Correlation between PRA and vasopressin secretion was absent.