BACKGROUNDS: The metabolic syndrome is the clustering of cardiovascular risk factors such as glucose intolerance, hypertension, dyslipidemia and visceral obesity. The National Cholesterol Education Program Adult Treatment Panel lll(NCEP ATP III) criterion for the diagnosis of metabolic syndrome is now widely used in many parts of the world. However, applying this criteria to an Asian population, could underestimate the prevalence of the metabolic syndrome. Especially anthropometric index such as waist circumference is inappropriate for Asian population. In 2000, the WHO Western Pacific Region recommended the cut-off value for obesity in Asians to body mass index(BMI) over 25.0kg/m2 and abdominal obesity to waist circumference(WC) over 90cm in men and 80 cm in women. But, among Asians, each ethnic group has their own anthropometric character, so it is difficult to apply the same criteria to different ethnic group in Asia. Thus, the aim of this study is to validate the appropriate cut-off value of WC to increase the risk of the metabolic syndrome in Korean adult population. METHODS: A total of 824 subjects(427 men, 397 women), aged 30~60 years(average 47.87.8 years), who underwent routine medical check-up in Korea Association of Health Promotion, were included in this study. The metabolic syndrome was defined as patients with three or more of the followings: Hypertriglyceridemia(=150mg/dL) low HDL-cholestetol(Male <40mg/dL, Female <50mg/dL) Hypertension(Taking antihypertensive medication or systolic blood pressure=130mmHg or diastolic blood pressure=85mmHg) Glucose intolerance(Taking oral hypoglycemic agent or fasting glucose =110mg/dL). RESULTS: The metabolic syndrome was seen in 21.7% of total subjects; glucose intolerance in 18.2%, hypertension in 56.4%, hypertriglyceridemia in 44.8%, and low HDL-cholesterolemia in 42.0%. With metabolic score, who had 0 components of metabolic syndrome in 16.7%, 2 components in 30.9%, 3 components in 18.0%, and all 4 components in 3.8 % of our enrolled subjects. The cut-off value of BMI to correspond with the metabolic syndrome by ROC curve was 24.8(sensitivity 63%, specificity 61%, p<0.001) in men and 24.9kg/m2(70%, 61%, p<0.001) in women. The cut-off value of WC was 86cm in men(65, 54%, p<0.001) and 82 cm in women(71, 60%, p<0.001). When the subjects were divided into 5 groups according to the WC, the odds ratio for the metabolic syndrome was 5.17(95% CI 2.11-12.67) in men and 16.94(2.17-132.41) in women with the cut-off value of 90cm in men and 85cm in women. CONCLUSION: We concluded that WHO Western Pacific Region recommendation guideline as a cutoff value of BMI for obesity in Korean adult was reasonable, but not of WC. Therefore, we recommended the modified cut-off value of WC for abdominal obesity in Korean adult to 90cm in men and 85 cm in women.