Optimal treatment of acute myocardial infarction (AMI) depends on the duration of the ischemia. The Anderson Wilkins (AW) electrocardiographic acuteness score has been shown to complement the historical timing in estimating the time interval from acute thrombotic coronary occlusion in patients presenting with chest pain and evolving myocardial infarction. The purposes of this study were to (1) compare the distributions of the previously developed AW acuteness score in a training population with either anterior or inferior AMI and (2) propose modifications to the formula to achieve distributions similar to the observed distributions of historical times from onset of pain.