A review of the research evidence on the mental health of serving and ex-Service military personnel in the UK up to September 2012. The aim of the review was to identify the main gaps and recommend key areas for future research and covered areas relating to: the prevalence of mental health problems in serving and ex-Service personnel, the treatment needs and barriers to seeking help, the most appropriate services for those with mental health problems, issues concerning transition and resettlement to civilian life and the impact on families and the support available to them. The project consisted of a literature review, grey literature analysis and interviews with key stakeholders.