The Third Report of the National Cholesterol Education Program Adult Treatment Panel III emphasized the importance of management of the metabolic syndrome. However, little information is available about the effect of weight reduction on the metabolic syndrome in obese patients among Koreans. A longitudinal clinical intervention study from the 12-week of weight reduction program, including life style modification and adjuvant appetite suppressants, in 78 obese persons was performed. Anthropometry and metabolic risk factors were measured before and after weight reduction. Visceral (VAT), subcutaneous (SAT), and total adipose tissue (TAT) on abdomen were determined by CT scan. Moderate decrease in weight (9.3%) induced significant reduction of waist circumference, systolic and diastolic blood pressure, and triglyceride. Weight reduction also resulted in significant decrease in total cholesterol, LDL-C, uric acid, fasting insulin, and HOMA score. The subjects with metabolic syndrome showed more improvements of metabolic components than those without metabolic syndrome through weight reduction. The reductions of visceral-subcutaneous fat ratio (VSR) and waist circumference were observed as for the predictable variables related to the improvement of metabolic component and insulin resistance in Korean obese patients.