Background: There are many factors affecting coronary artery atherosclerosis. The aim of this study was to evaluate the factors affecting plaque of LM in angiographic normal LM. Method: In forty patients(mean age 60.4짹10.3, male 28(70%)) with coronary artery disease(CAD), we evaluated the atherosclerosis risk factor and coronary angiography was taken. LM plaque was measured by intravascular ultrasound. We measured the maximal thickness and area of the plaque, percentage of the plaque area at 2mm intervals and calculated the average value. Result: There were 28(70%) patient in acute coronary syndrome(ACS) and 12(30%) patient in stable angina. There were 15(37.5%) hypertension, 6 (15.0%) diabetes, 20(50.0%) smoker and 12(30.0%) hypercholestrolemia. The patient with multivessel disease was ten(25.0%). The maximal thickness and percentage area of LM plaque for smoker(1.37짹0.56mm, 44.4짹12.7%) were significantly greater than non-smoker(0.92짹0.18mm p<0.01, 31.9짹6.8% p<0.01), The maximal thickness and percentage area of LM plaque for men(1.26짹0.51mm, 41.0짹12.7%) were significantly greater than women(0.89짹0.18mm p<0.01, 31.4짹6.1% p<0.01) but between sex and smoking, smoking was significant factor related to LM plaque burden by univariate analysis(p<0.01). The maximal diameter of LM plaque for ACS(1.24짹0.51mm) was significantly greater than stable angina(0.93짹0.29mm p<0.05). but there were no difference with diabetes, hypertension, hypercholesterolemia or not. There was no significant correlation between total cholesterol, triglyceride, HDL-C, LDL-C, apoprotein(a), apoprotein(b), extent of coronary artery disease and LM plaque burden. Conclusion: The smoking was important risk factor for LM plaque burden in patient with angiographic normal LM.