MIrreM examines estimates and statistical indicators on the irregular migrant population in Europe as well as related policies, including the regularisation of migrants in irregular situations. A core aim of the project is to address the uncertainty and contested nature of evidence on irregular migration by fostering a shared understanding of basic features of and policy options to address the phenomenon. MIrreM analyses policies defining migrant irregularity, stakeholders’ data needs and usage, and assesses existing estimates and statistical indicators on irregular migration in the countries under study and at the EU level. Using several coordinated pilots, the project develops new and innovative methods for measuring irregular migration and explores if and how these instruments can be applied in other socio-economic or institutional contexts. Based on a broad mapping of regularisation practices in the EU as well as detailed case studies, MIrreM will develop ‘regularisation scenarios’ to better understand conditions under which regularisation should be considered as a policy option. Together with expert groups that will be set up on irregular migration data and regularisation, respectively, the project will synthesise findings into a Handbook on data on irregular migration and a Handbook on pathways out of irregularity. The project’s research covers 20 countries, including 12 EU countries and the United Kingdom, involving stakeholders in the research. A core mandate of the project consists of engaging relevant stakeholders, including NGOs, service providers, migrant-led organisations, researchers and policymakers on local, national and EU levels in the research, in order to better take into account their needs and feed results from the project back into their work.