Twelve normotensive patients with coronary artery disease and stable effort-induced angina pectoris were selected: the antiischemic effect of captopril was studied. A maximal cycloergometer effort test was obtained before (base) and after administration of placebo or captopril (50 mg p.o.). The following parameters were measured: heart rate (HR), blood pressure (BP), maximal rate/pressure product (MRPP), maximal workload sustained, (MWS), maximal working time (MWT), and S-T depression at MRPP. The base and placebo were similar. Compared to them captopril augmented the MWT, increased the MWS, reduced S-T depression at MRPP, and decreased the number of patients with effort-induced angina pectoris. The antiischemic effect of captopril seems related both to its effect on HR and BP, and to a local enhancement of coronary blood flow.