Background and aim: Conflicting evidence exists surrounding the increased risk of adverse outcome conferred by preinjury anticoagulant and antiplatelet treatment in patients with head injury. The aim of this study was to determine the epidemiology of patients with head injury on anticoagulant and antiplatelet treatment admitted to a hospital from an emergency department (ED). Methods: This was a retrospective analysis of all patients with head injury admitted to a hospital from a major UK ED between 1 January 2005 and 31 December 2007. Results: 399 patients met the inclusion criteria. 110 patients underwent CT, with 24 having traumatic haemorrhage. Of 271 patients on aspirin, 75 (28%) underwent CT, with 19 of these (25%) having traumatic haemorrhage. Of 89 patients on warfarin, 27 (30%) underwent CT, with 4 of these (15%) having traumatic haemorrhage. Seven of the 24 (29%) patients with traumatic haemorrhage on CT did not undergo urgent ED scanning. All these patients were on aspirin. Conclusions: This study confirms the need for caution in the early discharge of patients with head injury taking anticoagulant medication. This study also raises concerns that patients taking antiplatelet medication prior to injury may also be at high risk of developing covert serious intracranial haemorrhage and suggests the need for a well-designed cohort study looking at antiplatelet risk in head injury.