This database was created in the framework of the EU-funded research project CLANDESTINO (2007-2009). The project has meanwhile expired; nevertheless, the need for transparent data on the size of irregular migration in the European Union remains vital. Irregular migration is a sensitive issue and continues to be high on the public and policy agenda. Notably policy makers at local, national and EU level, as well as NGOs in this field need to know the size of the social issue they deal with. Transparent data also is important for a realistic framing of public discussions. Therefore, former project researchers have agreed to continue and update the database.