Background; To investigate the prevalence of impaired glucose metabolism and its association with inflammation and insulin resistance (IR) in acute myocardial infarction (AMI) patients without a history of diabetes. Methods; We prospective enrolled 52 AMI patients, and 75-g oral glucose tolerance testing was performed on 30 patients at discharge and again 3 months later. We also measured serum adiponectin, high sensitive C-reactive protein, and IL-6 on both occasions. Data were compared with those of 30 type 2 diabetic patients without a history of AMI. Results; Forty percent and 36.7% of AMI patients had impaired glucose tolerance (IGT) at discharge and at 3 months, respectively. The corresponding proportions for newly diagnosed diabetes are 33.0% and 30.0%. At discharge, AMI patients with IGT or diabetes showed higher high sensitive C-reactive protein and IL-6 levels compared with AMI patients with normal glucose tolerance or control type 2 diabetic patients. AMI patients with IGT or diabetes exhibited higher IR and lower serum adiponectin levels than AMI patients with normal glucose tolerance at 3 months after discharge. Conclusion; Previously undiagnosed diabetes and IGT are common in Korean patients with AMI. These glycometabolic abnormalities are associated with inflammation, IR, and serum adiponectin levels. Oral glucose tolerance testing or periodic check of serum glucose needed to identify the risk of diabetes in AMI patients.