Background and Aims: High sodium intake has been known to elevate blood pressure and increase the incidence of cardiovascular disease. Thus dietary sodium reduction is the essential component in the management of hypertension, and nationwide approach to reduce sodium intake is now ongoing in Portugal, Finland and Japan. The aim of the present study is to evaluate the effects of dietary sodium reduction on blood pressure and to calculate the prevalence of sodium sensitivity in Korean. The present study is the first human study performed in Korea for dietary sodium reduction. Materials and Methods: The number of planned subject is 100 subjects with or without hypertension. All the subjects are admitted for 2 weeks. They are given low sodium DASH diet (100 mmol sodium/day) for the first week and high sodium DASH diet (300 mmol sodium/day) during the next one week. During the last day of each diet period, 24 hour ambulatory blood pressure and 24 hour urine electrolyte are measured and compared. Significant difference in mean blood pressure between each diet (4.3 mmHg, p<0.05) is defined as salt sensitivity (SS). The present study will be completed at the end of August 2009. Results: Interim analysis showed a significant elevation of blood pressure during night after high sodium diet, and 25% prevalence of SS in the studied population. Conclusion: Dietary sodium reduction reduces night blood pressure significantly. Certain proportions of subjects with salt sensitivity exist among Korean. The final results will be presented at the Annual Scientific meeting.