The quality of life (QL) was evaluated in a 6 month double-blind trial in six European countries. Patients with a sustained supine diastolic blood pressure (SDBP), phase V, of 95 mm Hg or more on bendrofluazide, 5 mg daily (or an equivalent dose of a thiazide diuretic) were randomised to additional pinacidil (n = 127), 25 mg up to 100 mg daily, or nifedipine (n = 130), 20 mg up to 80 mg daily. The treatment groups were similar at entry for QL scores, average DBP of 103 +/- 6 (SD) mm Hg, and average age of 56 +/- 10 (SD) years. Eighteen patients on pinacidil and 12 on nifedipine withdrew due to side effects, such as oedema (both drugs) and flushing (nifedipine). The maximum antihypertensive effect was achieved within 6 weeks and maintained, resulting in a significant fall in SDBP of 13.7 mm Hg on pinacidil and 15.5 mm Hg on nifedipine at the end of the trial. There was no significant difference in the antihypertensive effect. The target SDBP was achieved in 57% of pinacidil-and 63% of nifedipine-treated patients. The average number of symptomatic complaints fell in both groups, with significant decreases in the reporting of blurred vision and headaches on nifedipine. Complaints of growth of body and facial hair increased on pinacidil but there were no significant between-drug comparisons with respect to side effects. In measures of psychological well being, patients on pinacidil showed a significant (p less than 0.05) improvement in total and cognitive function scores compared to nifedipine.(ABSTRACT TRUNCATED AT 250 WORDS)