The effect of hydrochlorothiazide, propranolol, and enalapril on cognitive and motor function and quality of life (QOL) in hypertensive patients was studied. Patients > or = 55 years of age with asymptomatic essential hypertension were included in a randomized, double-blind, placebo-controlled, crossover study. Subjects discontinued their previous antihypertensive agents and started hydrochlorothiazide 25 mg, extended-release propranolol hydrochloride 120 mg, enalapril maleate 10 mg, or placebo. One capsule was taken for three days and then the dosage was doubled for the remainder of a four-week period. Subsequent crossover treatments were begun without a washout period. In each treatment phase, a battery of psychometric tests was used to assess cognitive and motor function and quality of life; all tests but one were self-administered via computer terminal. Pulse rate and blood pressure were recorded, and compliance was monitored by capsule count. Sixteen of 30 patients interviewed completed the trials; one additional patient was evaluated after receiving all treatments except hydrochlorothiazide. Mean +/- S.D. age of the subjects was 66 +/- 6.1 years; 10 were black and 7 white; 9 were men. Except for the hydrochlorothiazide group, blood pressure in the active treatment groups did not differ significantly from placebo; hydrochlorothiazide significantly reduced systolic but not diastolic blood pressure compared with placebo. Compared with placebo, hydrochlorothiazide was associated with fewer incorrect responses in a test of complex reaction time and with greater discriminant reaction time response rates; otherwise, no difference between groups was noted in cognitive or motor performance. There were no significant differences between active treatments and placebo on individual QOL measures.(ABSTRACT TRUNCATED AT 250 WORDS)