During myocardial ischaemia, either in chronic coronary insufficiency or the acute phase of myocardial infarction, the renin-angiotensin system is activated which, by its deleterious cardiac effects, aggravates the ischaemia. Angiotensin Converting Enzyme (ACE) inhibitors, by their indirect effects (improved conditions of left ventricular load, negative inotropism, attenuation of catecholaminergic stimulation), reduce myocardial oxygen consumption, and by their direct coronary vasodilator effect reduce myocardial ischaemia. In addition, by attenuating the formation of oxygen-free radicals, by participating in the inactivation of some of them and protecting the lysosomal membranes, they combat reperfusion injury. In the animal model of acute myocardial infarction, they reduce myocardial infarct size and the prevalence of reperfusion arrhythmias. In the clinical situation, their effects on the ischemic response to effort in anginal patients remain controversial, appear to be more marked in abnormalities of the coronary micro-circulation especially in syndrome X and in hypertensive heart disease. In ischemic heart disease, long-term treatment may be beneficial by their trophic coronary and myocardial effects and two large scale trials report a decrease in the recurrence of myocardial infarction with ACE inhibitors. In the acute phase of myocardial infarction if their possible actions on reducing the infarct size and reperfusion arrhythmias require further confirmation, they do limit expansion of the infarct and decrease early left ventricular dilatation. However, the appreciation of tolerance is variable and the timing of their introduction remains controversial.