AbstractMild traumatic brain injury accounts for 1% to 2% of emergency department visits in the United States. Up to 15% of these patients will have an acute intracranial lesion identified on head computed tomography; less than 1% of mild traumatic brain injuries will require neurosurgical intervention. Clinical research over the past decade has focused on identifying the subgroup of patients with mild traumatic brain injury with acute traumatic lesions on computed tomography and specifically those at risk for harboring a potentially catastrophic lesion. This research has been used to generate evidence‐based guidelines to assist in clinical decision making. There is no evidence to support the use of plain film radiographs in the evaluation of patients with mild traumatic brain injury. The utility of brain‐specific biomarkers is rapidly evolving, and a growing body of evidence supports their potential role in determining the need for neuroimaging. Clinical predictors for identifying patients with abnormal computed tomography have been established and, if used, may have a significant positive impact on traumatic brain injury–related morbidity and healthcare utilization in the United States. Patients with negative computed tomography are at almost no risk of deteriorating; however, they should be counseled regarding postconcussive symptoms and should be given appropriate written instructions and referrals at discharge. Mt Sinai J Med 76:129–137, 2009. © 2009 Mount Sinai School of Medicine