Brain injury is one of the most frequent accident types for children and young adults and therefore poses a major health problem. Even seemingly minor brain injuries have been associated with an increased risk of behavioural, psychiatric and social problems. However, little is known about the prevalence, cause and child and family risk factors for brain injury among children and young adults. Unfortunately, accurate data regarding prevalence of brain injuries is difficult to obtain. Most previous research has relied on hospital discharge information which may seriously underestimate the extent of this problem because many individuals with brain injury are not admitted to hospital. To overcome these difficulties, we will use information from a longitudinal study of a birth cohort of 1265 children. Data regarding accidental injuries has been gathered for these children and young adults at regular intervals, including retrospective reports and in many cases supporting hospital and GP records. Access to this information will enable us to investigate the prevalence, cause and risk factors for brain injury from birth to 25 years of age. Using the information generated in this study we expect to be able to produce details regarding the prevalence and age specific causes of brain injury from birth to early adulthood. Results of the study should fill an important gap in our understanding of the prevalence and cause of brain injuries among children and young persons.