A representative cross-sectional study in five German cities aims to examine mental health and risk and protective factors of different groups of migrants. The focus of the preliminary studies will be on the feasibility and practicability of the planned investigation. This might alert the research team to problems in collecting representative data on immigrants' mental health. The team will adapt and fine-tune the methods, especially the sampling method, if necessary. Additionally, the researchers will validate the instruments, the questions for the guided interviews and for the in-depth interviews, in accordance with an emic understanding of topics, concepts and language use.