BACKGROUND AND OBJECTIVES: It has been reported that the common carotid artery (CCA) intima-media thickness (IMT) correlates to angiographically determined coronary artery stenosis. The aim of this study was to evaluate the correlation between the carotid IMT and left main (LM) plaque using ultrasonography. SUBJECTS AND METHODS: In fifty patients (mean age 59.6+/-9.9, males 35 (70%)) with coronary artery disease (CAD), the risk factors of atherosclerosis were evaluated and coronary angiographs obtained. The carotid IMT was measured in the far wall of both CCAs, with a 10 MHz linear probe, and the value of the IMT was automatically calculated using programmed software (M'ATH, METRIS Co., Argenteuil, France). The LM plaque was measured by intravascular ultrasound. The maximal thickness, ratio of the maximal thickness, cross-sectional area (CSA) and burden of the plaque were measured at 2 mm intervals, and the average values calculated. RESULTS: In the right common carotid artery, the maximal IMT significantly correlated with the mean plaque CSA and plaque burden of the LM (r=0.375. p=0.007, r=0.408. p=0.003, respectively). The mean IMT significantly correlated with the plaque burden of the LM, but not with the mean plaque CSA of the LM (r=0.357. p=0.011, r=0.264. p=0.063, respectively). In the left common carotid artery, the maximal IMT was not significantly correlated with the mean plaque CSA and plaque burden of the LM (p=0.251, p=0.218, respectively). The mean IMT was not correlated with the mean plaque CSA and plaque burden of the LM (p=0.249, p=0.078, respectively). CONCLUSION: There was a significant correlation between the right CCA IMT and plaque burden of the LM in patients with CAD.