BACKGROUND: Previous studies often of short duration have raised concerns that antihypertensive therapy with diuretics and beta-blockers adversely alters levels of other cardiovascular disease risk factors. METHODS: The Systolic Hypertension in the Elderly Program was a community-based, multicenter, randomized, double-blind, placebo-controlled clinical trial of treatment of isolated systolic hypertension in men and women aged 60 years and older. This retrospective analysis evaluated development of diabetes mellitus in all 4736 participants in the Systolic Hypertension in the Elderly Program, including changes in serum chemistry test results in a subgroup for 3 years. Patients were randomized to receive placebo or treatment with active drugs, with the dose increased in stepwise fashion if blood pressure control goals were not attained: step 1, 12.5 mg of chlorthalidone or 25.0 mg of chlorthalidone; and step 2, the addition of 25 mg of atenolol or 50 mg of atenolol or reserpine or matching placebo. RESULTS: After 3 years, the active treatment group had a 13/4 mm Hg greater reduction in systolic and diastolic blood pressure than the placebo group (both groups, P<.001). New cases of diabetes were reported by 8.6% of the participants in the active treatment group and 7.5% of the participants in the placebo group (P=.25). Small effects of active treatment compared with placebo were observed with fasting levels of glucose (+0.20 mmol/L [+3.6 mg/dL]; P<.01), total cholesterol (+0.09 mmol/L [+3.5 mg/dL]; P<.01), high-density lipoprotein cholesterol (-0.02 mmol/L [-0.77 mg/dL]; P<.01) and creatinine (+2.8 micromol/L [+0.03 mg/dL]; P<.001). Larger effects were seen with fasting levels of triglycerides (+0.9 mmol/L [+17 mg/dL]; P<.001), uric acid (+35 micromol/L [+.06 mg/dL]; P<.001), and potassium (-0.3 mmol/L; P<.001). No evidence was found for a subgroup at higher risk of risk factor changes with active treatment. CONCLUSIONS: Antihypertensive therapy with low-dose chlorthalidone (supplemented if necessary) for isolated systolic hypertension lowers blood pressure and its cardiovascular disease complications and has relatively mild effects on other cardiovascular disease risk factor levels.