Eighteen pediatric patients who sustained traumatic brain injury were enrolled in a double-blind, crossover study comparing the effects of 3% saline and 0.9% saline infusions on raised intracranial pressure (ICP). After resuscitation, each patient received a bolus of each saline concentration, and ICP was monitored for 2 h. Initial mean ICP before 0.9% saline infusions equaled 19.3 mm Hg and averaged 20.0 mm Hg during the subsequent 2-h trials (p = 0.32). Baseline mean ICP before 3% saline administration equaled 19.9 mm Hg and averaged 15.8 mm Hg for 2 h postinfusion (p = 0.003). Central venous pressure did not change significantly in either group, nor did measurements of renal function. Serum sodium concentrations increased in all 18 trials of 3% saline. Maximal concentrations of serum sodium occurred 30 min after bolus administration of 3% saline. Three percent saline significantly reduces raised ICP after traumatic brain injury when compared with normal saline. Intravascular dehydration, as measured by central venous pressure, did not occur during the study period.