BACKGROUND: Metabolic syndrome (MS) distinguishes individuals at very high risk in coronary artery disease (CAD) patients. This study was to investigate whether MS could affect the severity of coronary atherosclerosis assessed by the coronary angiography and cardiovascular events in Korea. METHODS: We collected clinical, biochemical, and angiographic information in 448 consecutive patients (223 men and 225 women; age 58.6 짹 11.0 years) who underwent first coronary angiography from January, 2005. Metabolic syndrome was defined by the National Cholesterol Education Program (NCEP) Adult Treatment Panel (ATP) III. We applied WHO Asian Pacific Region criteria for abdominal obesity following as; waist circumference greater than 90 cm in men, 80 cm in women. Each of stenosis segments was scored from 0 to 3 depending on the most severe diameter stenosis according to the following system: 0 = normal, 1 = stenosis between 1% and 49%, 2 = stenosis between 50% and 99%, 3 = total occlusion. A coronary atherosclerosis score was generated as the sum of the scores in all segments. RESULTS: We found that MS was more frequently detected in 225 CAD patients than in patients with normal coronary artery. (62% vs. 41%, p < 0.001) Elevated blood pressure was the most frequent abnormality (64.4%), followed by abdominal obesity (62.9%) and low HDL (46.5%), glucose level (45.1%), increased TG (38.5%). As the number of biomarkers of MS –the MS score- increased, the atherosclerosis score did (r = 0.35, p < 0.01), and the MS score was correlated with log hs-CRP (r = 0.30, p < 0.01). Patients with MS presented more frequently as acute coronary syndrome compared with patients without MS (52.8% vs. 33.3%, p < 0.01). CONCLUSION: An increasing MS score was significantly related to more severe coronary angiographic alteration and higher frequencies of unstable angina, myocardial infarction. We could predict the severity of CAD and its complication in patients with angina using the MS score.