To compare 5 antihypertensive drugs and placebo for changes in quality of life (QL). To assess the relationship of lifestyle factors and change in lifestyle factors to QL in participants with stage I diastolic hypertension. The Treatment of Mild Hypertension Study (TOMHS) was a randomized, double-blind, placebo-controlled clinical trial with minimum participant follow-up of 4 years. It was conducted at 4 hypertension screening and treatment academic centers in the United States. The cohort consisted of 902 men and women with hypertension, aged 45 to 69 years, with diastolic blood pressures less than 100 mm Hg. Informed consent was obtained from each participant after the nature of the procedures had been fully explained. Sustained nutritional-hygienic intervention was administered to all participants to reduce weight, to reduce dietary sodium and alcohol intake, and to increase physical activity. Participants were randomized to take (1) acebutolol (n = 132); (2) amlodipine maleate (n = 131); (3) chlorthalidone (n = 126); (4) doxazosin mesylate (n = 134); (5) enalapril maleate (n = 135); or placebo (n = 234). Changes in 7 QL indexes were assessed based on a 35-item questionnaire: (1) general health; (2) energy or fatigue; (3) mental health; (4) general functioning; (5) satisfaction with physical abilities; (6) social functioning; and (7) social contacts. At baseline, higher QL was associated with older age, more physical activity, lower obesity level, male gender, non-African American race, and higher educational level. Improvements in QL were observed in all randomized groups, including the placebo group during follow-up; greater improvements were observed in the acebutolol and chlorthalidone groups and were evident throughout follow-up. The amount of weight loss, increase in physical activity, and level of attained blood pressure control during follow-up were related to greater improvements in QL. In patients with stage I hypertension, antihypertensive treatment with any of 5 agents used in TOMHS does not impair QL. The diuretic chlorthali-done and the cardioselective beta-blocker acebutolol appear to improve QL the most. Success with lifestyle changes affecting weight loss and increase in physical activity relate to greater improvements in QL and show that these interventions, in addition to contributing to blood pressure control, have positive effects on the general well-being of the individual.