(1) The excretion of aldosterone in the patients with essential hypertension was compared with that of normotensive patients in various experimental conditions with simultaneous measurement of urinary electrolytes.(2) Under basal condition sodium excretion was found to decrease with the elevation of blood pressure. Some of the hypertensive patients had a slightly increased excretion of aldosterone when compared with normotensive patients, but the urinary level of aldosterone had no correlation with respective sodium output in urine. No difference in potassium excretion was observed between the both groups.(3) During the restriction of sodium intake of 25mEq. per day, hypertensive patients had enhanced sodium conservation capacity with more pronounced increase of aldosterone excretion.(4) Following an infusion of 500ml. of 4 per cent saline solution, hypertensive patients responded with a marked water and sodium diuresis than did normotensive patients. (5) NaCl-loading and mineralocorticoid administration in hypertensive patients did not cause so significant suppression of aldosterone excretion as normotensive patients.(6) From the above results it can be concluded that there is some difference in the adaptive response of aldosterone excretion between normotensive and hypertensive patients.