Low doses of thiazide diuretics are effective in controlling isolated systolic hypertension in most elderly patients. These agents are well tolerated and do not appear to adversely affect quality of life. Biochemical adverse effects are minimal with low doses. Of greatest importance, thiazide diuretics are the only class of antihypertensives that has been shown to reduce risk of cardiovascular events in patients with isolated systolic hypertension. Recent studies showed all these advantages with both chlorthalidone and hydrochlorothiazide therapy, although low-dose hydrochlorothiazide may cause less hypokalemia in the elderly than does chlorthalidone.