This prospective observational cohort study enrolled children younger than 18 years of age with blunt torso trauma who were evaluated in 20 PECARN emergency departments. The overall objective of this study is to develop a clinical decision rule for appropriate use of abdominal computerized tomography (CT) scanning in children with blunt torso trauma (to include the chest, abdomen and pelvis). The goal of the study was a prediction rule to identify children at very low risk for intra-abdominal injuries undergoing acute intervention for who computed tomography (CT) could be obviated. The study was funded by the Centers for Disease Control and Prevention (1 R49 CE001002). A prediction rule consisting of 7 patient history and physical examination findings, without laboratory or ultrasonographic information, identifies children with blunt torso trauma who are at very low risk for intra-abdominal injury undergoing acute intervention. These findings require external validation before implementation.