Veterans Administration Cooperative Study Group on Hypertensive Agents: effects of age on treatment results. In three double-blind studies of 1,396 hypertensive patients, the age-related effects of hydrochlorothiazide or bendroflumethazide were compared with those of propranolol, nadolol, or captopril, given singly or in combination with a thiazide. Patients in each treatment group were divided into those aged 55 to 69 years and those aged under 55. Whereas no age-related differences were apparent with propranolol, nadolol alone, or captopril alone, in all three studies the blood pressure-reducing effect was found to be greater in the older group of thiazide-treated patients than in the younger thiazide-treated group. The antihypertensive drugs studied are at least as effective in older as in younger hypertensive patients and the antihypertensive response with diuretics is greater in older patients than in younger patients. 