AIMS: The severity of thoracic aortic atherosclerosis (TAA) is associated with the extent of coronary artery disease (CAD). The aim of this study is to quantitative this relationship by developing a novel atherosclerotic index. METHODS AND RESULTS: Two hundred and forty six consecutive patients underwent transesophageal echocardiography (TEE) and coronary angiography. A grading system was used to define the extent of TAA for individual segment of the thoracic aorta. TAA burden index (TAABI) was defined as the sum of the grading for each segment. Of the derived values TAABI had the greatest specificity and sensitivity in predicting CAD. A TAABI of greater than 6 was associated with 16-fold increase in the probability of CAD with a specificity of 88% and a sensitivity of 81%. The positive predictive value was 77% and the negative predictive value 90%. CONCLUSION: A TAABI value of greater than 6 accurately predicts the presence of CAD. Patients with no or mild TAA are at low risk of having angiographically significant CAD.