Exogenous steroid administration has been shown to increase post-traumatic nitrogen excretion in adults. Children sustaining head injuries and treated with steroids have previously been shown to have markedly increased total urinary nitrogen levels; the amount of nitrogen excreted is also directly related to the degree of injury, as evidenced by the Modified Injury Severity Score (MISS). It is unclear whether the increased protein breakdown in these patients is a result of the head injury or a result of the catabolic effects of steroids. Nineteen children aged 4–14 years, suffering head injuries, were prospectively studied. In ten children, management included steroid administration (1–1.5 mg/kg/day dexamethasone X 3–5 days); the remaining nine were similarly managed; however, without steroids. The groups were matched for age, weight, MISS, and Glasgow Coma Scale Score. The steroid-treated group showed a significantly higher urinary nitrogen excretion (mean, 256 ± 24 mg/kg/day) than the nonsteroid-treated group (mean, 172 ± 29 mg/kg/day) (p< 0.02). These data suggest that steroids potentiate an already accelerated post-traumatic catabolic response seen in children with head injuries. Our data suggest that steroid use, which is common, mandates aggressive nutritional support in the management of children with head injuries.