BACKGROUND: The metabolic syndrome (MS) has been known as one of potential risk factor of coronary artery disease (CAD). We studied the relation between the MS score -the number of markers including elevated blood pressure, triglycerides (TG), low HDL cholesterol, hyperglycemia and abdominal obesity- and the extent of atherosclerotic plaque in patient with CAD. METHODS: Patients with CAD revealed more than 50% stenosis on coronary angiogram were sequentially enrolled and underwent the intravascular ultrasound (IVUS) analysis at a constant speed of 0.5 mm/sec. The lumen area (LA), the vessel area (VA), and the plaque area (PA) were measured at 0.5-mm intervals within lesion and the plaque burden (PB), the % area stenosis (%AS) were assessed at the most narrowest point. The estimating plaque volume of the lesion was measured using echoPlaque 2 software. RESULTS: 283 patients with symptoms of CAD (208 men, mean age: 57짹11) were divided into 6 groups based on their MS scores (score: patients; 0: 45, 1: 86, 2: 67, 3: 61, 4: 16, 5: 8). A low HDL cholesterol level (47%) was the most frequently observed marker, followed by increased blood pressure (45%), TG (42%), waist circumference (30%), and fasting glucose (20%). An increasing MS score was significantly related to higher frequency of acute coronary syndrome (p=0.023). In 307 lesions, there was no relationship between the MS score and angiographic and IVUS severity of stenosis (LA and %AS) at the narrowest point. However, MS score was significantly correlated with VA (p=0.015), PA (p=0.041) and the plaque eccentricity index (p=0.001) at most narrowest point. For volumetric analysis, mean analysis slices was 36.2짹8.6 and atheroma volume averaged 312.4짹94.9 mm³. The atheroma volume was larger in subjects with higher MS scoring group (p=0.0031). CONCLUSIONS: Although stenosis severity was not different among MS score subgroups, volumetric measures of IVUS of disease burden were worse in subjects with higher MS scoring. Therefore, the MS score provides a clinically useful index of severity of MS and the extent of atherosclerotic disease.