Background: Sudden cardiac death by ventricular tachycardia (VT) or fibrillation (VF) is thought the most common cause of death in patients with acute myocardial infarction. Korea Acute Myocardial Infarction Registry (KAMIR) study has been supported by the Korean Circulation Society in the memorandum of the 50th Anniversary of the Korean Circulation Society since Nov 2005. Methods: On-line registry of acute myocardial infarction at the web site of www.kamir.or.kr has been performed in 42 primary percutaneous coronary intervention (PCI) centers in Korea. Between Nov 2005 and Apr 2006, 3,345 (2,328 male, 1,017 female; 63.7짹12.7 years) were enrolled in KAMIR. The epidemiologic study of ventricular tachycardia or fibrillation was performed. Results: One hundred thirty eight patients had ventricular tachyarrhythmia and the incidence of ventricular tachyarrhythmia was more common in male than in female patients (M:F=100:38, 65.2짹12.5 years, 5.9% of total enrolled patients, p=0.043). Ventricular tachycardia (112, 81.1%) was more common than ventricular fibrillation (26, 18.9%). Ventricular tachyarrhythmia developed in 75 (54.3 %) patients anterior wall myocardial infarction and in 53 (38.4%) patients with inferior infarction (p=0.082). Left ventricular ejection fraction was 43짹13 %. Fifteen (10.9%) patients had ventricular tachyarrhythmia at the time of admission, but 123 patients during PCI procedure or in-hospital stay. ST elevation myocardial infarction was more common (110, 79.7%) than non-ST elevation myocardial infarction (28, 20.3%, p=0.008). Four patients died of ventricular tachyarrhythmia. Conclusion: The Ventricular tachyarrhythmia was more common in male and in patients with ST elevation myocardial infarction according to Korea Acute Myocardial Infarction Registry.