Background The association between epicardial fat and coronary artery disease has not been evaluated. The objective of the present study was to evaluate the relationship of echocardiographic epicardial fat to the presence and severity of coronary artery disease in a clinical setting. Methods and Results Two hundred and three consecutive patients who underwent echocardiography and diagnostic coronary angiography were studied. The epicardial fat thickness on the free wall of the right ventricle was measured at end-diastole from the parasternal long-axis views of 3 cardiac cycles. Coronary angiograms were analyzed for the extent and severity of coronary artery disease using Gensini's score. The patients were divided into 2 groups according to the fourth quartile of epicardial fat thickness (Group I <7.6 mm; Group II ≥7.6 mm). There were no significant differences in the baseline characteristics except for waist circumference (p=0.023). Significant correlations were demonstrated between epicardial fat thickness and age (r=0.332, p<0.001), C-reactive protein (r=0.182, p=0.009), body mass index (r=0.142, p=0.044) and waist circumference (r=0.229, p=0.001). The patients with a higher epicardial fat thickness were associated with a high Gensini's score (p=0.014). Multivariate analysis showed that age (odds ratio (OR) 5.29, p=0.003), epicardial fat thickness (OR 10.53, p=0.004), diabetes (OR 8.06, p=0.006) and smoking (OR 14.65, p=0.015) were independent factors affecting significant coronary artery stenosis. Conclusions Epicardial fat thickness was significantly correlated with the severity of coronary artery disease in patients with known coronary artery disease. (Circ J 2007; 71: 536 - 539)