OBJECTIVE: To determine the incidence of vasospasm in children who have suffered moderate to severe traumatic brain injury. METHODS: A prospective observational pilot study in a 24-bed pediatric intensive care unit was performed. Twenty-two children aged 7 months to 14 years with moderate to severe traumatic brain injury as indicated by Glasgow Coma Score 120 cm/s were considered to have vasospasm by criterion A. If flow velocity in the MCA was >120 cm/s and the Lindegaard ratio was >3, vasospasm was considered to be present by criterion B. Patients with basilar artery (BA) flow velocity >90 cm/s met criteria for vasospasm in the posterior circulation (criterion C). RESULTS: In the MCA, 45.5% of patients developed vasospasm based on criterion A and 36.3% developed vasospasm based on criterion B. A total of 18.2% of patients developed vasospasm in the BA by criterion C. Typical day of onset of vasospasm was hospital day 2-3. Duration of vasospasm in the anterior circulation was 4 +/- 2 days based on criteria A and 3 +/- 1 days based on criteria B. Vasospasm in the posterior circulation persisted for 2 +/- 1 days. CONCLUSIONS: Using the adult criteria outlined above to diagnose vasospasm, a significant proportion of pediatric patients who have suffered moderate to severe traumatic brain injury develop vasospasm during the course of their treatment.