Background: Epidemiological, clinical and animal-experimental evidence shows a direct relationship between dietary sodium intake and blood pressure (BP). There was no study evaluated the relationship of 24 hour ambulatory BP and 24 hour urinary sodium excretion (24HrUNa) in Korean population. Methods: We analyzed data from two studies conducted in parallel at our clinical research center. The first study was primarily designed to evaluate the relationship of 24 hour ambulatory BP and 24HrUNa in volunteers (Korean Circulation Society 2010-2). The second study was to estimate the amount of 24HrUNa in representatives of a city population and calculate the expected average sodium intake in a city (11162KFDA162). To ensure random sampling of population from a city, participants were selected by random digit dialing method. Measurement of 24 hour ambulatory BP were performed in parallel with the collection of 24 hour urine sample. Central BP and brachial-ankle pulse wave velocity (baPWV) was also measured. Results: Among 645 participants, data from 416 subjects (46.9짹9.2 years) who were considered to collect sufficient urine samples corresponding to a 24-hour period, was analyzed (64.5%). Men (n=175, 46.9짹9.5 years,) showed higher 24HrUNa than women (n=241, 46.9짹9.1 years) (202.1짹76.6 vs 160.5짹60.0 mmol/day, p<0.001). Hypertensive subjects (n=202, 49.7짹8.1 years) had higher 24HrUNa than normotensive subjects (n=214, 44.3짹9.4 years) (188.9짹71.6 vs 167.6짹67.8 mmol/day, p=0.002). Highest tertile of 24HrUNa had high prevalence of hypertension and men. Multivariate linear regression analysis adjusted with age and smoking, showed significant correlation of 24HrUNa to 24 hour averaged systolic BP (SBP), diastolic BP (DBP) and mean BP (MBP). Daytime, nighttime and morning BP, aortic SBP (AoSBP), augmentation index and baPWV were also significantly correlated with urinary sodium excretion, but aortic pulse pressure (AoPP), and pulse pressure amplification (PPA) were not. Highest tertile of 24HrUNa showed higher 24 hour average SBP, DBP and MBP, and AoSBP and AoPP than the lowest tertile after adjustment with age, smoking and gender. Women showed similar result, but men didn���t. Conclusions: The present study showed the significant relationship of 24HrUNa and ambulatory blood pressure and AoSBP. This is the first study performed in Korea, evaluating the effect of high sodium intake on BP by 24 hour urinary analysis of sodium. The result of the present study could also be used to compare the amount of sodium intake in Korean population with the other countries.