Abstract. Background: Care of the severely injured child requires the rapid assembly of personnel trained in pediatric trauma care. Trauma team activation criteria, which are highly sensitive and maximally specific for identifying the child who requires resuscitation, are necessary to provide rapid care to all who need it, while using resources efficiently. Objective: To determine the sensitivity and specificity of the standard trauma team activation (TTA) criteria for identifying patients who receive resuscitation in the emergency department. Methods: A one-year study was conducted of all patients transported by emergency medical out-of-hospital services for a trauma-related complaint. For all patients, out-ofhospital medical control operators recorded whether patients met TTA criteria and, if so, which criteria were met. Criteria included standard physiologic, anatomic, and mechanism parameters. Sensitivity and specificity for the outcome of resuscitation (volume restoration, assisted ventilation or intubation, chest tube insertion/needle decompression, operative intervention) were calcuated. Results: A total of 492 patients met the case definition. Two-thirds were male, the mean age was 8 years (Ϯ4.8 SD), and the Injury Severity Score was Ն15 in 9.3%. Trauma team activation criteria were met by 179 patients (36.4%) and, of these, 107 met mechanism criteria only. A resuscitative intervention was received by 54 (10.9%) of the total and none in the mechanism-only group. Sensitivity and specificity of the TTA criteria for predicting receipt of a resuscitation procedure were 98.1% and 71.2%, respectively. When mechanism criteria were excluded, the sensitivity remained 98.1% and the specificity increased to 95.7%. Conclusions: Criteria for TTA that include patients who meet mechanism criteria only are not specific for identifying patients who receive a resuscitative intervention. Use of anatomic and physiologic criteria only results in an increase in specificity, thereby reducing overtriage while retaining a high sensitivity.