Most revascularization studies on acute myocardial infarction have included patients who have ST-segment elevation or new-onset left bundle branch block. However, the characteristics of patients who have non–ST-segment elevation acute myocardial infarction and who have undergone angiographic analysis of their infarct-related arteries have not been adequately described. This study suggests that these patients are likely to have had coronary bypass surgery (odds ratio 4.58, 95% confidence interval 1.83 to 11.5, p = 0.0012) and that circumflex artery occlusions are more likely to present as non–ST-segment elevation than as acute myocardial infarction with ST-segment elevation and/or left bundle branch block (odds ratio 2.91, 95% confidence interval 1.62 to 5.22, p = 0.0003).