To determine whether an angiotensin-converting enzyme inhibitor (lisinopril) or calcium channel blocker (amlodipine) is superior to a diuretic (chlorthalidone) in reducing cardiovascular disease incidence in sex subgroups, we carried out a prespecified subgroup analysis of 15 638 women and 17 719 men in the Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial (ALLHAT). Total follow-up (active treatment + passive surveillance using national administrative databases to ascertain deaths and hospitalizations) was 8 to 13 years. The primary outcome was fatal coronary heart disease or nonfatal myocardial infarction. Secondary outcomes included all-cause mortality, stroke, combined cardiovascular disease (coronary heart disease death, nonfatal myocardial infarction, stroke, angina, coronary revascularization, heart failure [HF], or peripheral vascular disease), and end-stage renal disease. In-trial rates of HF, stroke, and combined cardiovascular disease were significantly higher for lisinopril compared with chlorthalidone, and rates of HF were significantly higher for amlodipine compared with chlorthalidone in both men and women. There were no significant treatment sex interactions. These findings did not persist through the extension period with the exception of the HF result for amlodipine versus chlorthalidone, which did not differ significantly by sex. For both women and men, rates were not lower in the amlodipine or lisinopril groups than in the chlorthalidone group for either the primary coronary heart disease outcome or any other cardiovascular disease outcome, and chlorthalidone-based treatment resulted in the lowest risk of HF. Neither lisinopril nor amlodipine is superior to chlorthalidone for initial treatment of hypertension in either women or men. Clinical Trial Registration- clinicaltrials.gov; Identifier: NCT00000542.