Background: Gamma-glutamyltransferase (GGT) has been introduced to be a new prognostic factor for cardiovascular diseases and is associated with inflammatory and metabolic markers in patients (pts) with metabolic syndrome. We investigated whether serum GGT level would help to detect subclinical myocardial dysfunction in coronary artery disease pts with preserved left ventricular (LV) systolic function. Methods and Results: We analyzed routine laboratory findings including GGT and echocardiographic parameters in 103 hospitalized pts who complained of chest pain (56 unstable angina, 47 stable angina, 73 males, 61.1 짹 9.1 years old) with preserved LV systolic function (LV ejection fraction > 50%). In our study, mean GGT was 34.4 짹 29.0 IU/L, mean alanine-aminotransferase (ALT) was 28.6 짹 29.3 IU/L, respectively. The mean LV ejection fraction was 64.9 짹 7.0 % and early mitral inflow velocity to early diastolic mitral annular velocity (E/E���) was 11.9 짹 5.0. GGT was significantly correlated with ALT (r=0.487, p<0.001), aspartic acid transaminase (AST) (r=0.374, p<0.001), glucose (r=0.285, p<0.01), triglyceride (r=0.203, p<0.05), free fatty acid (r=0.261, p<0.01), uric acid (r=0.266, p<0.01), left atrium volume index (r=0.332, p<0.001), deceleration time (r=-0.311, p<0.001) and E/E��� (r=0.301, p<0.001). In multiple linear regression analysis, GGT were independently correlated with E/E��� even after adjustment for age, body mass index, ALT, triglyceride (beta coefficient= 0.260, p<0.01). The optimal cutoff of GGT for E/E > 15, suggestive of elevated LV filling pressure was 28 IU/L (AUC 0.662, CI 0.511-0.813, sensitivity 65%, specificity 61.5%, p<0.05). Conclusion: We found a novel correlation between GGT and E/E��� in coronary artery disease pts with preserved LV systolic function. This finding raises the possibility that GGT may be associated with elevated LV filling pressure even before evidence of clinical myocardial dysfunction can be detected in these pts.