Head injury is a major cause of morbidity and mortality in all age groups. Injury to the head can result in traumatic brain injury (TBI) of varying severity. TBI is common, with a self-reported lifetime prevalence of up to 40% in adults.1 Currently, there is no effective treatment to reverse the effects of the primary brain injury sustained, and treatment is aimed at minimising the secondary brain injury that can occur due to the effects of ischaemia, hypoxia and raised intracranial pressure. This can occur immediately, within the following hours or days, or after a further head injury. An understanding of the epidemiology of head injury is essential for devising preventive measures, to plan population-based primary prevention strategies and to provide effective and timely treatment, including provision of rehabilitation facilities to those who have suffered a head injury. This information can then be used to improve TBI outcomes.