Objectives : The purpose of this study was to find the prevalences and risk factors of the metabolic syndrome according to Sasang constitution. Methods : The medical records of 364 subjects who had taken health examinations and diagnosis of Sasang constitution from January to June of 2003 at a health examination center of a hospital in Seoul were reviewed. The prevalences and the risk factors of the metabolic syndrome according to Sasang constitution were compared and analyzed. Results : 1) Among the 364 subjects, 88 (24.2%) were Soeumin, 101 (27.7%) were Soyangin, and 175 (48.1%) were Taeumin. 2) The prevalences of high WC, high TG, low HDL-c, high BP and high FBS of Taeumin were significantly higher than those of the other constitutions (p-value < 0.05). 3) The prevalence of the metabolic syndrome of Taeumin, Soyangin, and Soeumin were 46.3%, 16.8% and 9.1% respectively. The rates were significantly different according to Sasang constitution (p-value < 0.001). 4) Taeumin had higher risk of high WC than Soeumin (adjusted OR : 3.83, 95% CI : 1.19-12.29) and higher risk of high FBS than Soeumin (adjusted OR: 5.93,95% CI : 1.11-31.77). 5) Taeumin had higher risk of the metabolic syndrome than Soeumin (adjusted OR : 3.40, 95% CI : 1.25-9.23). Conclusions : There were significant differences in the prevalence of metabolic syndrome according to Sasang constitution. Sasang constitution was identified as an independent risk factor of metabolic syndrome.