Vivid descriptions of reactions to traumatic events span many centuries, although their nature has changed over time.1 Post-traumatic stress disorder was first recognised as a diagnosable psychiatric disorder in the third edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-III)^w1 and ICD-10 (International Classification of Diseases, 10th edition).2 Its very existence continues to attract debate, with several authors arguing that culturally determined, understandable emotions to traumatic events are being pathologised.^w2 However, even its most ardent critics are more concerned by overdiagnosis than by whether post-traumatic stress disorder should be used as a label for the severe mental health problems some people experience after traumatic events.3 This article provides an overview of our current understanding of the disorder, who it affects, and the best approaches to its prevention and management.