Patients with mild traumatic brain injury constitute the overwhelming majority of head-injured patients seen in the emergency department. The indications for radiologic imaging in these patients are still undergoing study and revision. The Glasgow Coma Scale is a widely used triage score for head injury, but is less useful at identifying which patients with mild head injuries have intracranial pathology. There have been several retrospective studies and a few prospective studies examining the indications for imaging in mild to moderate head trauma. They all show that it is not easy to predict which patients will have CT abnormalities, and that some of these patients do go on to require neurosurgery. No set of clinical predictors have yet been put together that is capable of identifying all patients who are safe to be discharged without a CT scan. Pharmacologic therapy to help reduce axonal damage after head trauma and thus minimize the postconcussive sequelae of mild traumatic brain injury remains a challenge for physicians and neurobiologists into the next century.