Abusive head trauma (AHT) is the leading cause of traumatic death and disability in early childhood, affecting at least 690,000 children annually in the United States. AHT is missed or unrecognized in 30% of head-injured children and more than 25% of children with unrecognized AHT suffered additional inflicted injuries. Ten percent of children with unrecognized AHT subsequently died or were killed—80% of whom could have been saved by earlier recognition of abuse.8 A flawed decision to launch an abuse evaluation can increase parental stress, expose the child to additional risks, prolong hospital stays, and increase health care costs.9,10 Doctors who care for young victims of trauma must make important decisions to launch or forgo child-abuse evaluations when presented with head-injured children. These decisions can be difficult, and the stakes are high. Unfortunately, doctors routinely struggle to define a “reasonable suspicion” of abuse and have demonstrated inherent biases related to child age, race, marital status, and socioeconomic status. The principal investigator (Hymel) conceptualized, designed, and directed sequential multicenter studies to derive and validate an effective AHT screening tool in the form of a clinical decision rule (CDR)—an evidence-based tool developed specifically to guide a discrete decision in the continuum of AHT care. Though the CDR has shown promise in preliminary studies, it has not yet been subjected to a formal randomized trial, which is the purpose of this project. The proposed CDR trial will demonstrate the CDR's impact on AHT screening accuracy, hypothesizing that CDR application will increase AHT detection and reduce unnecessary abuse evaluations. We will conduct a stratified cluster randomized trial (SCRT) at eight US pediatric intensive care units (PICUs) randomly assigned to intervention (n = 4) or control (n = 4) conditions. The SCRT will compare AHT screening accuracy after the deployment of active multifaceted implementation strategies designed to promote CDR acceptance, utilization, and accuracy at the intervention sites (Aim 1). In addition, the SCRT will determine what—if any—site-, provider-, and patient-specific factors predict CDR application in PICU settings (Aim 2). Once the SCRT has concluded, we will conduct a 12-month sustainability trial at intervention sites, systematically repealing the implementation strategies one by one to discern their relative importance to sustainability (Exploratory Aim 3). We anticipate that this simple, inexpensive, and reliable CDR will decrease the negative impacts of physicians' inherent biases and practice disparities, significantly increase AHT detection, decrease unnecessary abuse evaluations (and their associated risks), and reduce AHT-associated healthcare costs. Most importantly, the CDR will save lives—the lives of children who will otherwise suffer additional fatal inflicted injuries if/when their AHT is missed or unrecognized.