The aims of this study were to compare the prevalence of the metabolic syndrome according to the WHO and NCEP ATP III criteria in Korean adults, and to compare the prevalence of the metabolic syndrome with the results in previous Korean studies. The study comprised 1,230 subjects (627 men, 603 women) aged 30-79 years (mean 52.4 +/- 10.3 years) who underwent medical check-up from April to June, 2001 in the Korea Association of Health (KAH). The prevalence of the metabolic syndrome according to the modified WHO criteria was 21.8 % of men and 19.4 % of women. However, the prevalence was increased 1.6 times (34.2 % ) in men and 2.0 times (38.7 % ) in women using the modified NCEP criteria. The prevalence of the metabolic syndrome has varied widely according to differences in the criteria. Thus, further studies are necessary to define the appropriate criteria of the metabolic syndrome for Korean adults.