Patients were recruited through office-based practices and hypertension clinics which were reimbursed by the Clinical Trials Center on a per-patient basis. Six hundred patients were entered into the vanguard or feasibility phase and a total of 42,448 were entered into the full-scale trial. The primary hypothesis of the antihypertensive trial was that the combined incidence of fatal coronary heart disease and nonfatal myocardial infarction would be lower in hypertensive patients randomized to amlodipine (a calcium antagonist), lisinopril (an angiotensin-converting enzyme (ACE) inhibitor), or doxazosin (an alpha adrenergic blocker) as compared to those randomized to chlorthalidone (a thiazide-like diuretic). Secondary endpoints were total cardiovascular mortality, major morbidity, all-cause mortality, and health-related quality of life.