Several experimental studies have suggested that the sulphydryl-containing angiotensin-converting enzyme inhibitor, captopril, has cardioprotective effects in the setting of acute myocardial ischaemia, ischaemia/reperfusion and infarction. We have observed that captopril can reduce the degree of dilatation and early functional myocardial infarct expansion produced by 3 h of permanent coronary artery occlusion in anaesthetized, open-chest dogs. In addition, captopril has been shown to limit experimental infarct size, reduce the incidence of reperfusion arrhythmias, and improve contractile function of stunned myocardium. When administered chronically after myocardial infarction, both experimental and clinical evidence suggests that captopril reduces left ventricular dilatation. Captopril is currently being tested in large clinical trials as adjuvant therapy to thrombolysis.