The antihypertensive efficacy and safety of quinapril 20mg plus hydrochlorothiazide 6.25mg were compared over 8 weeks with captopril 50mg plus hydrochlorothiazide 15mg in 52 patients with mild to moderate essential hypertension (27 men and 25 women age 49.7 ± 8.4 years). The study also evaluated the relationship between antihypertensive efficacy and plasma renin activity/blood pressure sensitivity to changes in dietary sodium intake. The combination of quinapril or captopril with hydrochlorothiazide showed similar antihypertensive effects and tolerability. Neither blood pressure salt sensitivity nor renin profile were predictive of blood pressure response to either therapy. These results suggest that the antihypertensive efficacy of an angiotensin converting enzyme inhibitor when administered in fixed ratio with a thiazide diuretic is independent of salt sensitivity in hypertension.