To investigate the potential anti-ischaemic effects of benazepril (10 mg bid) in comparison to placebo, this new ACE-inhibitor was given to 11 patients with chronic stable angina, reproducible exercise-induced ST-segment depression and angiographically verified coronary artery disease. Blood pressure at rest, plasma renin activity, and plasma concentration of atrial natriuretic peptide were measured after treatment periods of two weeks. Bicycle exercise tests at the same time should evaluate ST-segment depression at comparable maximal workload, work capacity, blood pressure, and heart rate at exercise. In comparison to placebo, benazepril reduced arterial blood pressure significantly from 140 +/- 14/90 +/- 11 mm Hg to 125 +/- 16/84 +/- 10 mm Hg (p less than 0.05) and increased plasma renin activity from 2.19 +/- 3.76 ng/ml/h to 9.62 +/- 8.49 ng/ml/h (p less than 0.005). In contrast, ST-segment depression decreased only slightly and not significantly from 2.09 +/- 1.22 mm to 1.91 +/- 1.00 mm. Benazepril had neither an effect on the frequency of episodes of angina pectoris nor did it reduce the amount of GTN-consumption. Also, work capacity and plasma concentration of atrial natriuretic peptide were not changed in comparison to placebo. Although the significant reduction of blood pressure and the highly significant increase of plasma renin activity demonstrate the specific action of benazepril, a significant anti-ischaemic effect could not be established.