Funded by the Barrow Cadbury Trust, this report presents an analysis of the costs of traumatic brain injury (TBI), with particular reference to the links between head injury and crime. The first two chapters examine the scale and consequences of TBI, highlighting the relatively young age of many victims and the wide-ranging and long-lasting nature of the disabilities that may result. Chapter 4 looks at the economic costs of TBI, focusing the losses of output resulting from people’s inability to work and on the costs to health and social services in relation to treatment, rehabilitation and long-term care. It then considers the links between TBI and offending, and the evidence which shows that TBI can lead to cognitive and behavioural changes such as impaired judgement, reduced impulse control and increased aggression. It then sets out some of the costs of crime to society as a whole. The report finds that adolescence is a peak period for both offending and head injury. The final chapter presents estimates of the long-term costs of a case of head injury. For a 15-year-old in the general population it estimates the cost is around £155,000 per case; and for a 15-year-old coming into contact with the criminal justice system estimates are at around £345,000 per case. It highlights the opportunity intervention, covering both preventive measures and the early provision of evidence-based treatment for head injury, particularly among young people in the criminal justice system.