Background Ventricular tachycardia(VT) and atrial fibrillation(AF) have been linked to an increased risk for in-hospital and long-term mortality rates in patients with acute myocardial infarction(AMI). Obesity and metabolic syndrome are increasing and known to play an important role in cardiovascular morbidity and mortality. Previous studies have reported that obesity is a risk factor for postoperative atrial fibrillation and ventricular tachyarrhythmia in patients with AMI and heart failure. However, it is unknown obesity and metabolic syndrome(MS) increase the risk of arrhythmia in patients with AMI. Methods We prospectively analyzed the association between obesity and MS and the incidence of cardiac arrhythmia in a total of 113 patients with AMI. 24-h Holter monitoring was performed 6짹2 days after AMI. We divided the patients into 2 categories according to their BMI(kg/m2) and evaluated the existence of MS. Fat computed tomography was done to evaluate the association of central obesity and arrhythmia in 50 patients. Results 56(49%) were obese(body mass index ���25kg/mg2) and 82(72%) had a MS. Paroxysmal AF occurred 33(28%) of the patients and VT occurred 6(5%) of the patients. In these patients, MS was significantly associated with high incidence of AF (61% versus 17%, P=0.003), but there was no difference in occurrence of VT. There was no difference between mild ( body mass index ���25kg/mg2) obese and non-obese patients in occurrence of AF and VT. The patients with central obesity in fat CT had no association with the occurrence of AF and VT. 寃곕�� Metabolic syndromeis an importantand modifiable risk factor for AF especially in the patients with acute myocardial infarction.