Background: The optimal glycosylated hemoglobin (HbA1c) level in acute MI patients remained to be controversial era, but may be especially important in predicting the prognosis of acute MI patients underwent percutaneous coronary intervention (PCI). The aim of this study was to identify the predictive value of preprocedural HbA1c levels and diabetes mellitus (DM) for cardiac events during mid-term follow-up period in patients complicated by acute myocardial infarction (MI) and underwent PCI. Methods: A total of 1,449 consecutively hospitalized patients between January 2008 and May 2010 were included. The study populations were acute MI patients underwent PCI and followed up during 12 months period. Patients were stratified according to history of DM and, further, according to whether they had a HbA1c level >6.5 %. The influence of cardiac risk factors, medications, angiographic findings, and interventional procedures were analyzed, and Cox proportional hazard analysis was used to determine the influence of HbA1c on mid-term mortality. Major adverse cardiac events (MACEs) included total cardiac death, recurrent myocardial infarction, revascularization procedures. Results: In patients without a history of DM, HbA1c level ���6.5 % in 865 patients (Group 1) and >6.5 % in 147 (Group 2). Of these with DM, HbA1c level were ���6.5 % in 108 (Group 3) and >6.5 % in 329 (Group 4). Rate of MACEs were significantly higher in Group 3 (14.0% vs. 19.5% vs. 31.6% vs. 17.5%, respectively, p = 0.029). By multivariate analysis using Cox regression, HbA1c (HR = 1.032; 95% CI = 0.632-1.684, p = 0.901) and DM (HR = 1.046; 95% CI = 0.571-1.917, p = 0.884) were not associated with patients outcome. Conclusions: This study suggested that HbA1c or DM is not a predictor of cardiac events in acute MI patients underwent PCI. It is thought that this result can support, at least in part, that long term hyperglycemia during pre-intervention period may not influence mid-term MACE in AMI era. Keywords: glycosylated hemoglobin ▪ diabetes mellitus ▪ myocardial infarction ▪ prognosis