The anti-ischemic effect of a single oral dose of 10 mg of enalapril maleate (E) was investigated in 14 normotensive patients with coronary artery disease (CAD) and stable effort-induced angina pectoris. An exercise stress test was performed three times in each patient at the same clock hour on three successive days: with no treatment (baseline), 6 h after administration of placebo (P), and 6 h after oral administration of a single 10 mg dose of E. The multistage nonstop effort tests were performed in the sitting position. Workload started at 25 W and was increased by 25 W every 2 min until an ischemic ST depression of more than 1.5 mm was observed. The following parameters were measured: heart rate (HR), systolic blood pressure (BP), rate-pressure product (RPP), workload sustained (WS), elapsed time of effort (ET), and millimeters of ischemic ST depression. The values of the parameters observed with baseline, P, and E were compared at the moment of appearance of chest pain or ischemic ST depression, at the moment of maximal effort, maximal common WS (MCWS), and maximal common RPP (MCRPP). Enalapril delayed the appearance of the ischemic ST depression. At the MCWS, the RPP was significantly lower under E and the ST depression was less marked; this effect was the result of a lower BP level, in the absence of any significant change in HR response. The acute effects of E observed in normotensive patients with effort-induced angina pectoris seems to be related to the inhibition of angiotensin at the coronary level and to its antiadrenergic action.