A history of deliberate self-harm (DSH) is one of the main indicators for suicide. There has been a rise in the number of presentations to emergency departments as a result of DSH, predominantly among 15 to 24 year olds. The main risk factors for this are risk-taking behaviour, substance misuse and interpersonal conflict, often occurring in combination in the 24 hours before the self-harm occurred. Studies of adolescents identify family, friends and school to be the main sources of support in preventing suicidal behaviour, proving more important than help from external agencies. Support and guidance for families and friends may therefore be valuable. Repeated presentation with DSH to the emergency department can signify an underlying problem that is not being identified or addressed, leading to recurrent crises. National early-intervention programmes involving screening for risk factors, and brief intervention in emergency departments, could be cost-effective interventions.