Women with acute myocardial infarction are less likely than men to receive thrombolytic therapy. It is not known whether sex-related differences in the presenting 12-lead electrocardiogram (ECG) account for this relative underutilization of acute reperfusion therapy in women. The authors examined the initial ECGs of 188 men and 185 women matched for age and history of previous acute myocardial infarction randomly selected from the Myocardial Infarction Triage and Intervention registry who presented with 4 hours of confirmed acute myocardial infarction. There were no sex-related differences in the number of leads with ST elevation, the presence of diagnostic ST elevation, or the overall magnitude of ST elevation. In addition, there was no sex-related difference in associated ECG findings that might effect physicians' utilization of acute reperfusion therapy, including the location of ST elevation (anterior vs inferior), the presence of abnormal Q waves in leads with ST elevation, the association of ST depression with ST elevation (reciprocal changes), or the presence of confounding factors, such as bundle branch block or hypertrophy. Differences in the presenting ECG do not explain the underutilization of acute reperfusion therapy in women.