Inhibitors of angiotensin converting enzyme (ACE) were tried in patients early after myocardial infarction (MI) irrespective of the severity of circulation insufficiency. Monopril was used in 23 patients in the dose 7.6 mg/day. Ednit was given to 21 patients in the dose 5.3 mg/day. Control groups included 19 and 21 patients, respectively. All the patients underwent treadmill test and echocardiography on MI day 1 and 13-14. ACE inhibitors provide better exercise tolerance and favourable course of MI even in the absence of marked manifestations of cardiac failure though left ventricular ejection changed insignificantly. They may also prevent myocardial ischemia. The difference between monopril and ednit effects was insignificant.