Objective. Delay in the provision of definitive care for critically injured children may adversely effect outcome. We sought to speed care in the emergency department (ED) for trauma victims by organizing a formal trauma response system. Design. A case-control study of severely injured children, comparing those who received treatment before and after the creation of a formal trauma response team. Setting. A tertiary pediatric referral hospital that is a locally designated pediatric trauma center, and also receives trauma a victims from a geographically large area of the Western United States. Subjects. Pediatric trauma victims identified as critically injured (designated as 'trauma one') and treated by a hospital trauma response team during the first year of its existence. Control patients were matched with subjects by probability of survival scores, and were chosen from pediatric trauma victims treated at the same hospital during the year preceding the creation of the trauma team. Interventions. A trauma response team was organized to respond to pediatric trauma victims seen in the ED. The decision to activate the trauma team (designation of patients as 'trauma one') is made by the pediatric emergency medicine (PEM) physician before patient arrival in the ED, based on data received from prehospital care providers. Activation results in the notification and immediate travel to the ED of a pediatric surgeon, neurosurgeon, emergency physician, intensivist, pharmacist, radiology technician, phlebotomist, and intensive care unit nurse, and mobilization of an operating room team. Most trauma one patients arrived by helicopter directly from accident scenes. Outcome Measures. Data recorded included identifying information, diagnosis, time to head computerized tomography, time required for ED treatment, admission Revised Trauma Score, discharge Injury Severity Score, surgical procedures performed, and mortality outcome. Trauma Injury Severity Score methodology was used to calculate the probability of survival and mortality compared with the reference patients of the Major Trauma Outcome Study, by calculation of Z score. Results. Patients treated in the ED after trauma team initiation had statistically shorter times from arrival to computerized tomography scanning (27 ± 2 vs 21 ± 4 minutes), operating room (63 ± 16 vs 623 ± 27 minutes) and total time in the ED (85 ± 8 vs 821 ± 9 minutes). Calculation of z score showed that survival for the control group was not different from the reference population (z = -0.8068), although survival for trauma-one patients was significantly better than the reference population (z = 2.102). Conclusion. Before creation of the trauma team, relevant specialist were individually called to the ED for patient evaluation. When a formal trauma response team was organized, time required for ED treatment of severe trauma was decreased, and survival was better than predicted compared with the reference Major Trauma Outcome Study population.