OBJECTIVES: A small number of patients with minor head injury deteriorate, resulting in serious injury or death. Clinical features are often used to identify which patients with minor head injury are likely to deteriorate and therefore need CT scanning.  To estimate the value of these characteristics for diagnosing intracranial injury (including the need for neurosurgery) in adults, children and infants, a systematic review and meta-analysis of diagnostic accuracy was undertaken.  METHODS: Citations were identified through electronic searches of several key databases, including MEDLINE, from inception to March 2010. Cohort studies of patients with minor head 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. Study selection, quality assessment and data extraction were performed by one reviewer and checked by at least another. Where results allowed, pooled sensitivity, specificity and likelihood ratios were estimated through meta-analysis. RESULTS: Data were extracted from 71 studies (with cohort sizes ranging from 39 to 31694 patients).  The most useful clinical characteristics for identifying those with intracranial injury were depressed or basal skull fracture in both adults and children (positive likelihood ratio [PLR], >10).  Other useful characteristics in adults or children 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 haematoma and scalp laceration in children. Few studies were undertaken in children and even fewer reported data for neurosurgical injuries.  CONCLUSIONS: Amongst other characteristics, depressed or basal skull fracture indicated increased risk of intracranial injury and the need for CT scanning in adults and children. Other characteristics, such as headache in adults and scalp laceration of haematoma in children, do not reliably indicate increased risk.