1. Backgrounds and Aims Human being is divided into 4 constitution types(Taeyangin, Soyangin, Taeumin, and Soumin). According to Sasang Constitutional Medicine[SCM] Each constitution has its own incidence, treatment and prevention of disease. The purpose of this study is to find the relation of dietary habits, life styles and Psychosocial stress with obesity in each Sasang Constitution. 2. Methods 975 subjects who have received health examinations and diagnosis of Sasang Constitution at Kyung-hee Medical Center were divided into each constitutional group. Each constitutional group was then divided into obese group and normal group. We evaluated risk factors of obesity such as dietary habits, life styles, and Psychosocial stress. These data were statistically analysed to investigate the relations between risk factors and obesity. And then significant factors were analysed by multinomial logistic regression analysis to get each odds ratio. 3. Results In a multinomial logistic regression analysis adjusted for age and sex, promotion of appetite and overeating or excessive diet elevated risks of obesity in Taeumin, promotion of appetite and high speed of diet elevated risks of obesity in Soyangin, and Psychosocial stress elevated risks of obesity in Soeumin. 4. Conclusions The results suggest that promotion of appetite and overeating or excessive diet may be major risk factors for obesity in Taeumin, promotion of appetite and high speed of diet in Soyangin and Psychosocial stress and dyschezia in Soeumin.