Like many other West European metropolises, since the early 1960s Vienna has been a target for the migration of guest workers from the Balkan. Guest workers from the former multi-national Yugoslavia are not only the oldest, but if based on numbers, also the most important group of immigrants in Vienna. The neighbourhoods of this group of immigrants are also unequally distributed throughout the metropolis. Ethnic segregation is a social-spatial phenomenon that occurs in all large cities. The population from former Yugoslavia belongs to one of the lowest classes of the worker migration, and it is still concentrated above all in neighbourhoods with older buildings and low living standards.