Background: The detection of an abnormal electrocardiogram (ECG) is often the first clue to the presence of hypertrophic cardiomyopathy (HCM). The most frequent changes include left atrial enlargement (LAE), left ventricular hypertrophy (LVH), giant negative T wave (GNT) in precordial leads, etc. Purpose: The aim of this study is to clarify the ECG characteristics of HCM in Korean. Method: From Jan. 1998 to Jun. 2005, 234 (0.55%) patients were diagnosed as HCM consecutively in Dongsan Medical Center. Among them, the echocardiography and ECG in 218 analyzable patients were reviewed. The patients were divided to three morphologic pattern of hypertrophy; group 1 – apical HCM (APH), group 2 –mixed form, group 3- asymmetric septal HCM (ASH). Results:The ECG characteristics are described in the following table. GNT was observed in 58 (26.6%) patients. GNT was most frequently located at the V4 lead, and then V5, V3. The relationship between the apical thickness and GNT voltage was not significant (p=0.473). Conclusions:Well known characteristics of ECG in HCM were not different between the groups except AF and GNT. The difference of AF might be related to the age. GNT was more frequent in APH. However, ASH group had higher incidence of GNT than we had expected.