Which patients with an acute myocardial infarction should be treated with an angiotensin-converting enzyme (ACE) inhibitor and when should this treatment be initiated? Combining pathophysiological evidence with the findings of large clinical trials, it is recommended that in the postinfarction setting ACE inhibitors should be given only to high risk patients, ie, patients with arterial hypertension, patients in Killip class II or III, patients with an acute anterior myocardial infarction, patients with left ventricular dysfunction and patients with a previous myocardial infarction. Treatment should be started as soon as it is considered safe.