Northern Ireland (NI) has one of the highest rates of suicide in the UK and, unlike other countries; the rate among young men has been increasing in recent years. Only 28% of individuals who die by suicide in NI have been in touch with health services. The majority, therefore, are unknown to health and social services and may not be receiving the help they need. There is a need to understand the risk factors for suicide so that interventions can be targeted to those most at risk. Interest is increasing in the biological and social factors which may influence suicide risk including existing physical illness or exposure to suicide in the family. The study aims to utilize data on the family from the 2001 Census linked to death data from the GRO in the subsequent decade to determine if exposure to death by suicide in the family is associated with an increased risk of suicide in the individual.