The importance of the criterion of Quality of Life (QOL) for compliance with antihypertensive drugs led us to study the QOL of 51 hypertensives receiving 2.5 mg of the new formulation of prazosin (sustained release), compared with 49 subjects treated by a converting enzyme inhibitor (enalapril 10 mg), in a double-blind randomized trial. QOL, assessed by means of a 22 item self-administered questionnaire, improved significantly with prazosin, during the 24 weeks of the trial. In the intention to treat analysis, the global score of QOL increased from 46.3 +/- 8.4 to 51.6 +/- 8.9 (p < 0.0001); the covariance analysis showed that the improvement was obtained as early as the 8th week. A similar favourable evolution was observed for anxiety, retardation and anhedonia components, computed from the same questionnaire. No significant difference in QOL evolution was found between prazosin and enalapril. Both treatments proved equivalent in respect of efficacy on blood-pressure values, and tolerance, estimated through the number of dropouts or side-effects. These results confirm the benefit to QOL of hypertensive patients of the new formulation of prazosin.