The rationale for using angiotensin converting enzyme (ACE) inhibitor therapy after acute myocardial infarction has been largely founded on observations made in experimental situations, and in humans before the routine introduction of reperfusion therapies. An important area of ongoing debate therefore continues to be the role of ACE inhibition as an early adjunct to attempts to achieve and maintain patency of infarct-related coronary arteries. Data from clinical trials indicate a substantial survival benefit in patients with impaired ventricular function, but provide little support for the routine treatment of the remaining majority of patients. An important issue in determining whether these agents should be used in a more general and long-term secondary prevention role, is their potential ability to prevent subsequent reinfarction. However, such a strategy is unlikely to be enhanced by either immediate initiation of treatment or withdrawal after just 1 month of therapy.