The obesity epidemic in children makes it plausible that prevalence rates of elevated blood pressure (BP) are increasing over time. Yet, previous literature is inconsistent because of small sample sizes. Also, it is unclear whether adjusting for risk factors can explain longitudinal trends in prevalence of elevated BP. Thus, we analyzed a population-based sample of 3248 children in National Health and Nutrition Examination Survey (NHANES) III (1988-1994) and 8388 children in continuous NHANES (1999-2008), aged 8 to 17 years. Our main outcome measure was elevated BP (systolic BP or diastolic BP ≥ 90th percentile or systolic BP/diastolic BP ≥ 120/80 mm Hg). We found that the prevalence of elevated BP increased from NHANES III to NHANES 1999-2008 (Boys: 15.8% to 19.2%, P=0.057; Girls: 8.2% to 12.6%, P=0.007). Body mass index (Q4 versus Q1; odds ratio=2.00; P<0.001), waist circumference (Q4 versus Q1; odds ratio=2.14; P<0.001), and sodium (Na) intake (≥ 3450 mg versus <2300 mg/2000 calories; odds ratio=1.36; P=0.024) were independently associated with prevalence of elevated BP. Also, mean systolic BP, but not diastolic BP, was associated with increased Na intake in children (quintile 5 [Q5] versus quintile 1 [Q1] of Na intake; β=1.25 ± 0.58; P=0.034). In conclusion, we demonstrate an association between high Na intake and elevated BP in children. After adjustment for age, sex, race/ethnicity, body mass index, waist circumference, and sodium intake, odds ratio for elevated BP in NHANES 1999-2008 versus NHANES III=1.27, P=0.069.