Steroidal lactones have been reported to produce sodium diuresis and potassium conservation in primary or secondary aldosteronism1,2. When given with a thiazide compound, they always reduced potassium excretion and increased that of sodium.3 Spironolactone, synthesized by Cella and Kagawa blocks the urinary electrolyte effects of desoxycorticosterone acetate in rats.4 Similarly, it blocks the renal effects of aldosterone presumably through a direct antagonizing action.5 In hypertensive patients with unrestricted sodium intake, spironolactone is hypotensive according to Hollander, Chobanian and Wilkins.6 The present study was undertaken to determine the oligemic and antihypertensive effects of spironolactone* in non-edematous hypertensive patients with, or without, other antihypertensive therapy and compare them with those obtained with hydrochlorothiazide † alone or in combination with this steroid. Methods Used Seven patients hospitalized in the Research Ward of the Cleveland Clinic Hospital were used for this study; 4 had essential hypertension which in one