It the time of actual discussion on illegal migration in Europe it is important to analyze which behaviors constitutes the phenomenon. Therefore the first part of the article indicates the behaviors that are called the illegal migration. They are: illegal border crossing, use of fraudulent documents or illegal stay. Author made the legal analysis trying to state if those acts are forbidden by law, especially referring to Polish criminal and administrative law. The second part presents the dynamics and structure of phenomenon in the period of last five years. The structure presents the nationalities of immigrants and the routes leading to Europe.W dobie aktualnej dyskusji nad problemem nielegalnej migracji w Europie warto pochylić się nad an...