Clinical features can be used to identify which patients with minor brain injury need CT scanning. A systematic review and meta-analysis was undertaken to estimate the value of these characteristics for diagnosing intracranial injury (including the need for neurosurgery) in adults, children, and infants. Potentially relevant studies were identified through electronic searches of several key databases, including MEDLINE, from inception to March 2010. Cohort studies of patients with minor brain injury (Glasgow Coma Score [GCS], 13-15) were selected if they reported data on the diagnostic accuracy of individual clinical characteristics for intracranial or neurosurgical injury. Where applicable, meta-analysis was used to estimate pooled sensitivity, specificity and likelihood ratios. Data were extracted from 71 studies (with cohort sizes ranging from 39 to 31,694 patients). Depressed or basal skull fracture were the most useful clinical characteristics for the prediction of intracranial injury in both adults and children (positive likelihood ratio [PLR], >10). Other useful characteristics included focal neurological deficit, post-traumatic seizure (PLR >5), persistent vomiting, and coagulopathy (PLR 2 to 5). Characteristics that had limited diagnostic value included loss of consciousness and headache in adults and scalp hematoma and scalp laceration in children. Limited studies were undertaken in children and only a few studies reported data for neurosurgical injuries. In conclusion, this review identifies clinical characteristics that indicate increased risk of intracranial injury and the need for CT scanning. Other characteristics, such as headache in adults and scalp laceration of hematoma in children, do not reliably indicate increased risk.