Despite the tendency for harmonisation of strategies for mental health care delivery, rules and regulations for involuntary placement or treatment of mentally ill persons still differ remarkably internationally. Rapid European integration and other political developments require valid and reliable international overviews, sound studies and profound analyses of this controversial issue. To give an overview of compulsory admission data from official sources across the European Union (EU). Data on the legal frameworks for involuntary placement or treatment of people with mental illness and their outcomes were provided and assessed by experts from all EU member states. Total frequencies of admission and compulsory admission rates vary remarkably across the EU. Variation hints at the influence of differences in legal frameworks or procedures. Time series suggest an overall tendency towards more or less stable quotas in most member states. Further research is greatly needed in this field. Common international health reporting standards are essential to the compilation of basic data.