Six hundred and twenty-six male patients with mild to moderate hypertension were enrolled in a multicentre randomized double-blind clinical trial to determine the effect of methyldopa, captopril and propranolol on the quality of life of these patients. During the 6-month trial hydrochlorothiazide was added to the treatment programme of those patients whose blood pressure was not normalized. More individuals in the captopril group (33%) required hydrochlorothiazide than in the propranolol group (22%). As a group, those individuals who required a diuretic were heavier and had higher basal and end-of-study blood pressure than those individuals requiring only monotherapy. However, the basal quality-of-life indices were similar in the six treatment subgroups. The withdrawal rate from the study was twice as high for those patients treated with propranolol and methyldopa as for those treated with captopril, whether a diuretic was added or not. More individuals requiring a diuretic experienced sexual dysfunction and a substantial worsening of their general well-being and of physical symptom indices over the 24 weeks of the study (P less than 0.01), particularly in the captopril and propranolol treatment subgroups. In summary, the present results suggest that diuretic therapy may have a greater negative impact on the quality of life of hypertensive patients than captopril, propranolol or methyldopa alone.