OBJECTIVES: The aims of this study were to evaluate the prevalence, complications, and mortality of hypernatremic dehydration in neonates and to compare the effect of correction rate at 48 hours on mortality and on neurological outcome in the short term. METHODS: This retrospective study was conducted between January 2007 and 2011 in the neonatal intensive care unit. Term neonates were included. The patients were grouped as follows: group 1 = 150 to 160 mmol/L, group 2 = 161 to 170 mmol/L and group 3 = 171 to 189 mmol/L. RESULTS: Among 4280 neonates, 81 cases (1.8%) had hypernatremic dehydration. Groups 1, 2, and 3 consisted of 55, 23, and 3 patients, respectively. Mortality rates were as follows: 3.6%, 17.3%, and 66.6%. Mean serum sodium (Na) correction rates at 0 to 24 hours and 24 to 48 hours were 0.48 ± 0.2 versus 0.38 ± 0.31 mmol/L per hour (group 1) and 0.49 ± 0.21 versus 0.52 ± 0.28 mmol/L per hour (group 2), respectively. In 32 patients (58.1%) from group 1 and in 13 patients (56.5%) from group 2, correction rate of 0.5 mmol/L per hour or less was achieved. Twenty-two patients developed convulsions, which was the most common complication during therapy. Serum Na greater than 160 mmol/L at admission (odds ratio, 1.9; 95% confidence interval, 1.3-3.7) and serum Na correction rate of greater than 0.5 mmol/L per hour (odds ratio, 4.3; 95% confidence interval, 1.2-6.5) were independent risk factors for death or convulsion. There was a significant difference between groups 1 and 2 in Denver Developmental Screening Test II results (64.1% vs 30.7 %, P = 0.001). CONCLUSION: Hypernatremic dehydration is an important problem that should be managed properly to avoid adverse outcomes. Copyright © 2013 by Lippincott Williams &Wilkins.