Background: Hypertrophic cardiomyopathy (HCM) has diverse electrocardiographic (ECG) manifestations including ST segment elevation (STE). We investigated the prevalence of STE and echocardiographic parameters related to STE in patients with HCM Methods:Consecutive 118 patients(42 women,61짹13yrs)patients who had HCM from 2004 to 2006 were included.Standard 12–lead ECG in each patient was analyzed in regard to type, location, degree of STE and T wave morphology. Prevalence of left ventricular hypertrophy (LVH) by Romhilt-Estes(R-E) voltage criteria, Cornell criteria and Sokolow-Lyon(S-L) index was investigated. Patients with atrial flutter/fibrillation, coronary artery stenosis (diameter stenosis��� 50%), acute myocardial infarction and those who were taking antiarrhythmic drug were excluded. 93 Patients(35 women,60짹14yrs)were grouped into those with STE with biphasic T wave (group I, n=7), those with STE and no biphasic T wave (group II, n=11) and those without STE (group III, n=75).Results: There was no difference in demographics among groups. Posterior wall thickness was lower in group I compared with other groups (9짹2 vs.12짹3 vs 11짹3 mm, p=0.044). Ratio of septal to posterior wall thickness was significantly higher in group I compared with other groups (2.0짹0.5 vs 1.4짹0.5 vs 1.6짹0.5,p=0.023). There was no difference in pattern of HCM (apical: septal: diffuse) among groups (0:7:0 vs 4:7:0 vs 14:59:2, p=NS). Prevalence of positive ECG criteria of LVH by R-E was different from other groups (0 vs 55 vs 47%, p=0.045). Prevalence of positive Cornell criteria (43 vs 73 vs 64% p=NS) and S-L index (43 vs 73 vs 57%, p=NS) were not different among groups. Patients in group I had ST elevation in V1-3 leads (2 patients), V2-4 (3 patients) or V4-6 (2 patients).Three patients in group I presenting with acute chest pain had normal coronary angiogram .Patients in group II had ST elevation in V1-3 leads (10 patients) or inferior leads (1 patient).Conclusions:18 of 93 HCM patients (19%) had STE. Seven of those patients have a distinctive precordial ST segment elevation with biphasic T wave. HCM should be included in differential diagnosis of ST elevation syndrome.