A large simple placebo controlled trial, among adults with head injury and impaired consciousness, of the effects of a 48-hour infusion of corticosteroids on death and neurological disability. CRASH was a randomised, controlled, double-blind trial undertaken in 239 hospitals in 49 countries. A total of 10008 adults with head injury and a Glasgow Coma Score (GCS) of 14 or less within 8 hours of injury were randomly allocated 48 hour infusion of corticosteroids (methylprednisolone) or placebo. Primary outcomes were death within 2 weeks of injury or disability at 6 months. Prespecified subgroup analyses were based on injury severity (GCS) at randomisation and on time from injury to randomisation and analysis was by intention to treat. Access to this dataset is available via https://freebird.lshtm.ac.uk/