Background: Clinical and electrocardiographic (ECG) features of ventricular fibrillation (VF) in the absence of structural heart disease remain imprecise. Methods: We analyzed ECG features of 83 case subjects with idiopathic VF (IVF) from 11 centers in Korea. IVF was diagnosed after exclusion of structural heart disease, coronary artery spasm and other known channelopathies. Atypical Brugada syndrome (BS) was defined as BS ECG pattern that failed to satisfy the proposed diagnostic criteria of BS. Early repolarization was defined as J point elevation in two consecutive inferior or lateral lead with ��� 1mm ST segment elevation. Results: 1. Seventy three men and 10 women were included with a mean age of 45짹14 years. The baseline ECGs remote from VF episodes in patients with IVF were atypical BS in 18, early repolarization in 29, right precordial J wave in 21, male pattern ST elevation in V1 to V3 in 12, completely normal ECG without any J wave in 3. 2. During follow-up period, dynamic J wave change was recorded in 33 (40%) patients with IVF. 3. The magnitudes of dynamic J wave were variable. 4. All these features were transient, and many of the atypical BS, early repolarization, right precordial J wave, and male pattern ST elevation patients just showed ���normal��� ECG pattern until the typical accentuation of ER pattern of appearance of prominent J waves. Conclusion: ECG features of patients with IVF include atypical BS, inferolateral early repolarization, right precordial J wave, and male pattern ST elevation. J wave augmentation may be a common denominator.