Children deprived of their liberty and placed in detention are at extreme risk of violence, according to the U.N. Secretary-General’s Study on Violence against Children (the U.N. Study). Based on its global research, the U.N. Study identifies the following as the main sources of violence in both industrialized and developing countries: (1) violence by staff in detention institutions; (2) violence while in custody of police and security forces; (3) violence as a sentence; (4) violence by adult detainees; (5) violence by other children; and (6) self-harm, including self-mutilation and suicidal behavior. The research shows that in all the participating countries, Belgium, England and Wales, France, and the Netherlands, more effective and more transparent data collection and publication is required. One of the key problems identified in this study was the lack of data and information on the numbers of children deprived of their liberty and their conditions. The fundamental aim of this research was to develop a set of ‘violence indicators’ to improve data collection and analysis across Europe. It is hoped that the violence indicators developed through this research will enhance and complement the application of these juvenile justice indicators. Annex