Knowledge of left ventricular ejection fraction (LVEF) after acute myocardial infarction (MI) helps stratify risk and guides the use of evidence-based treatment such as angiotensin-converting enzyme (ACE) inhibitors and (3-blockers and revascularization. Indeed, studies demonstrated positive associations between LVEF measurement and use of ACE inhibitor therapy after MI. Furthermore, data underscore the pivotal role of LVEF in the selection of candidates for an automatic implantable cardioverter-defibrillator. Within this framework, current guidelines for the management of patients with MI emphasized the importance of LVEF assessment before discharge, and the report of American Heart Association(AHA)/American College of Cardiology (ACC) Conference on the Assessment of Healthcare Quality in Cardiovascular Disease and Stroke underscored the need to monitor LVEF measurement among patients with MI as a quality-of-care indicator. In contrast with the evidence supporting LVEF measurement after MI, little is known about actual utilization rates of tests to do so, how it may have evolved over time, and what determines its use in practice. The present study was undertaken to address these gaps in knowledge and assess the trends in the use of testing for LVEF after an incident MI in Olmsted County between 1979 and 1998.