High dietary salt intake was reported to increase blood pressure by numerous studies, but no study has investigated the effect of dietary salt intake on blood pressure variability (BPV). This study aimed to determine if daily salt intake is related to ambulatory BPV. The study included 136 primary hypertensive patients (92 male, 44 female) with a mean age of 50.7 +/- 11.1 years. All the patients underwent 24-h ambulatory blood pressure monitoring to determine both the 24-h systolic and 24-h diastolic BPV. 24-h urine sodium was measured. The correlation between BPV and 24-h urinary sodium was investigated. Logarithmic transformation of 24-h urinary sodium [log(24-h urinary sodium)] was positively correlated with the mean 24-h systolic ARV, and nighttime systolic ARV (r=0.371 and p=0.001, r=0.329 and p=0.028, respectively). Similarly, log(24-h urinary sodium) was positively correlated with mean 24-h diastolic ARV and nighttime diastolic ARV (r=0.381 and p=0.001, r = 0.320 and p=0.020 respectively). Log(24-h urinary sodium) was an independent predictor of BPV based on multivariate regression analysis. Dietary salt intake might play a role in the pathogenesis of ambulatory BPV. (C) 2016 Sociedad Espanola de Nefrologia. Published by Elsevier Espana, S.L.U.