Objectives: The purpose of the this study was to evaluate lifestyle intervention program for the treatment of the metabolic syndrome. Methods: Subjects of this study were 700 adults with metabolic syndrome who took health examinations in health promotion centers of Korea Association of Health Promotion between May 1 and June 30, 2006. Subjects were randomly assigned to an experimental group and a comparison group. Participants in the experimental group received intensive 3-month lifestyle modification intervention and participants in the comparison group received minimal information on lifestyle modification. Pre test and Post test were carried out to evaluate the effectiveness of the intervention program. Results: After the intensive intervention on lifestyle modification(healthy diet, physical activity, moderate drinking, stress management, and smoking cessation), the levels of blood pressure, waist circumference, fasting blood glucose and triglycerides were significantly reduced for those in experimental group(P<0.001). For those in comparison group, the levels of blood pressure(P<0.001), waist circumference(P<0.001), and triglycerides(P<0.01) were significantly reduced after the intervention. No change in the levels of high-density lipoprotein cholesterol were observed in both groups. After 3-month intervention, the prevalence of metabolic syndrome was reduced to 35.7% in experimental group and 48.5% in comparison group. Conclusion: This study has demonstrated the efficacy of therapeutic lifestyle intervention for the management of metabolic syndrome.