Objective: We investigated the association between office (OBP) and daytime ambulatory blood pressure (ABP) and sodium dietary intake and renal handling, as assessed by 24-hour urinary sodium excretion (24hUVNa) and endogenous lithium clearance (FELi), respectively. Design and method: We recruited from general population 192 individuals, never treated with antihypertensive medications. We administered standardized questionnaires to obtain information on subjects’ medical history and life style. SpaceLab 90207 monitors were programmed to measure blood pressure each 15 min during daytime (6:00–22:00) and each 30 min night-time. In adjusted categorical analyses, normotension was the referent group (OBP < 140/90 and daytime ABP < 135/85 mmHg). White-coat hypertension was defined as OBP > = 140/90 and daytime ABP < 135/85 mmHg; masked hypertension as OBP < 140/90 and daytime ABP > = 135/85 mmHg; and sustained hypertension as OBP > = 140/90 and daytime ABP > = 135/85 mmHg. Blood and 24-hour urine samples were collected. We calculated fractional excretion of lithium (FELi) as the marker of proximal sodium handling. A higher FELi indicates that less sodium and water is reabsorbed in the proximal tubule. Results: The study group included 87 men and 105 women, mean age 40.5 years, office BP 124.3/84.0 mm Hg, 24hUVNa 160 mmol/24 h, 128 (66.7%) normotensives, 29 (15.1%) sustained hypertensives, 8 (4.2%) individuals with masked hypertension, 27 (14.0%) subjects with white coat hypertension. In adjusted analyses, we did not find any associations between office or daytime ambulatory BP and 24hUVNa (P > = 0.24) or FE Li (P > = 0.30). However, in categorical multivariate analyses, individuals with masked hypertension had higher 24hUVNa as compared to normotensives (197 vs 153 mmol/24 h; P = 0.04). There were no differences in 24hUVNa between white-coat hypertensives (P = 0.59) or sustained hypertensives (P = 0.44) and normotensive reference group. None of BP categories differed from normotensives in terms of FELi (P > = 0.19). Conclusions: Excessive sodium intake may play a part in the genesis of masked hypertension in the general population.