Background and Objectives: A giant negative T wave on electrocardiogram is useful index to diagnose apical hypertrophic cardiomyopathy (AHCM). We hypothesize that giant T wave may represent more severe apical thickening in AHCM. Thus, this study was aimed to evaluate the differences of apical hypertrophy in patients of AHCM with or without giant T wave. Subjects and Methods: We selected 45 patients (65 짹 8 years, female 26) who were recently diagnosed as AHCM by echocardiogram. Typical AHCM was defined as spade shaped left ventricle with apical hypertrophy (���15 mm). The patients were divided into two groups: group 1 (AHCM with giant T), group 2 (AHCM without giant T). Apical wall thickness (WT) was measured at 4 segments and apical cross sectional muscle area (CSMA) was evaluated by tracing apical myocardium. Results: Eighteen patients (40%) had giant negative T wave (>10 mm). The tallest R wave of group 1 and 2 were 40.9 짹 10.3 and 29.7 짹 10.2 mV, respectively, p=0.001. The deepest T of group 1 and 2 were 12.6 짹 3.1 and 5.3 짹 2.4 mV, respectively, p<0.001. The maximal apical WT of group 1 and 2 were 18.9 짹 2.7 and 17.5 짹 2.6 mm, p=0.085. The apical CSMA of group 1 and 2 were 11.1 짹 1.6 and 9.2 짹 1.8 cm2, p< 0.002. Conclusion: The present study indicates that the presence of giant T wave in AHCM may represent more severe apical hypertrophy which has been shown by measuring of apical cross sectional muscle area.