In a study of 5 hypertensive patients (under strict metabolic conditions) it was observed that when sodium intake was moderately restricted (50 mEq/day about 3 gm. of sodium chloride) and dietary potassium was near average (50 mEq/day), 50 mg. of hydrochlorothiazide daily produced a satisfactory decline in blood pressure without causing problems of electrolyte imbalance. When dietary sodium was increased to 100 mEq/day, it was necessary to increase hydrochlorothiazide to 100 mg/day to maintain a comparable satisfactory antihypertensive response, but this dosage produced a deficiency of potassium which was offset by increasing dietary potassium to 100 mEq/ day. Thus, the desirable program for treatment of uncomplicated hypertension appears to be low doses of hydrochlorothiazide, moderate salt restriction, and a potassium-enriched diet.