Background: Vulnerable plaque in coronary artery can progress to plaque rupture and thrombosis, and have a strong potential to induce acute coronary syndrome. Many studies have demonstrated that metabolic syndrome (MS) is associated with increased risk for cardiovascular diseases and related mortalities. This study aimed to determine the predictive value of MS on the vulnerable plaque in the patients with stable angina pectoris. Methods: From September 2007 to June 2010, a total of 239 patients with stable angina pectoris who underwent coronary angiogram and intravascular ultrasound were categorized into two groups: Vulnerable plaque (VP) group (n=28, 21 men, 60.9짹9.5 years) and non-VP group (n=211, 133 men, 62.2짹9.1 years). NCEP-ATP III guideline was used to determine the presence of MS and each component of MS were compared between two groups. Results: VP group showed more frequent target lesion in proximal segment (p=0.014) of the coronary artery, and lower level of apolipoprotein-A1 (117.5짹20.6 mg/dL vs. 125.8짹20.2 mg/dL, p=0.043) than non-VP group. In addition, high density lipoprotein (HDL) cholesterol level as the criteria of MS (male< 40mg/dL, female< 50mg/dL) was observed in VP group more than non-VP group (p=0.039), but the prevalence of MS and other components of MS were not different between two groups. In IVUS, plaque burden was more abundant (76.9짹7.7% vs. 70.5짹9.7%, p=0.001), and plaque plus media cross-sectional area (P&M CSA) of minimum lumen site (13.0짹6.9 mm2 vs. 9.6짹3.9 mm2, p=0.024), P&M CSA of largest necrotic core site (13.8짹5.7 mm2 vs. 10.2짹3.6 mm2, p=0.01) and necrotic core in largest necrotic core site (3.0짹1.6 mm2 vs. 2.0짹1.1 mm2, p=0.019) were larger in VP group than non-VP group. Multivariate analysis using logistic regression for the presence of VP showed that the independent predictors are the low HDL cholesterol level (relative risk=2.998, 95% confidence interval=1.185-7.583, p=0.02) and abundant plaque burden (relative risk=1.084, 95% confidence interval=1.019-1.153, p=0.011). Conclusions: Although MS was not the predictor of vulnerable plaque, low HDL cholesterol level as the criteria of MS was meaningfully associated with vulnerable plaque.