1. Objectives The purpose of this study was to find out prevalence of chronic diseases according to Sasang constitutional. 2. Methods The medical records of 1,453 subjects who have taken health examinations and diagnosis of Sasang constitution from January 2003 to June 2003 at a health examination center of a university hospital in Seoul were reviewed. Sociodemographic factors and the prevalences of chronic diseases according to Sasang Constitution are compared and analyzed. 3. Results (1) Among the 1,453 subjects, 683(47.0%) were Taeumin, 421(29.0%) were Soyangin, and 349(24.0%) were Soeumin. (2) The prevalences of gastric polyp, diabetes mellitus, obesity, hypertension, hyperlipidemia, dyslipoproteinemia, abnormal liver function and fatty liver of T aeurnin were significantly higher than those of the other constitutions (p-value<0.05). And the prevalences of hepatic cyst and gall stone disease of Taeumin were higher than those of the other constitutions(p-value<0.l). (3) The prevalences of liver cirrhosis of Soyangin was significantly higher than that of the other constirutions(p-value <0. 05). (4) The prevalences of pulmonary tuberculosis on X-ray and anemia of Soeurnin were significantly higher than those of the other constitutions (p-value<0.05). And the prevalences of gastric xanthelasma and hypothyroidism of Soeumin were higher than those of the other constitutions(p-value<0.1). 4. Conclusions There were significant differences on the prevalences of some chronic diseases according to Sasang wnstirution.