In 2005, the International Diabetes Federation (IDF) presented a new, clinically accessible worldwide definition of 'metabolic syndrome' in a global consensus statement. According to the criteria, central obesity is an essential, not optional, component of metabolic syndrome, which is assessed by ethnicity- and gender-specific cut-off values as measured by waist circumference (WC). Thus we need to have a Korean population-specific WC cut-off values. For this aim, we analyzed data from the 1998 Korean National Health and Nutrition Survey from 6562 participants (2930 men and 3632 women). We determined the appropriate WC cut-offs using receiver operator characteristic (ROC) curve analysis giving the optimal sensitivity and specificity. We estimated multivariate-adjusted odds ratios (ORs) for risk (≥2metabolic risk factors assessed by IDF) according to the WC categories.The ROC curve analysis indicated that WC was better than BMI in predicting risks. Age-adjusted ORs for having ≥2metabolic risk factors increased abruptly for WC of 90cm in men and 85cm in women, indicating ORs greater than 5.0. WC-compatible 80th percentile was 90cm for men and 86.5cm for women. This analysis demonstrated the appropriate cut-off values of WC for abdominal obesity among Korean are 90cm for men and 85cm for women. These values may be updated, as new data become available.