This study aimed to estimate nationwide prevalence of the metabolic syndrome and to identify its association with cardiovascular diseases. The data on a national representative sample of 6,147 adults from 1998 Korea National Health and Nutrition Survey were analyzed. The syndrome was determined according to two kinds of modified definition from ATP III, in which abdominal obesity was determined by waist circumference (WC) standard for Asians and waist-to-hip ratio (WHR). Based on the former, prevalence was 22.1% in men and 27.8% in women. However, based on the latter, prevalence was 28.6% and 27.8%, respectively. Although age-specific prevalence was higher in men than in women among the younger group, it became higher in women among the older group because of its steeper rise with age. In multiple logistic regression, the syndrome was found to be positively associated with cardiovascular diseases (adjusted odds ratios (ORs)1.97 by WC and 1.48 by WHR in men, and 1.54 and 1.31 in women). Moreover, its effect size exceeded that of total cholesterol (adjusted ORs 1.21 in men, and 1.08 in women) or LDL cholesterol (1.58 in men and 1.22 in women). It is obvious that the metabolic syndrome prevails in Korea, and its importance regarding cardiovascular diseases is considerable. Prevention strategies should be implemented immediately to avoid cardiovascular epidemic in the near future.