After the EU enlargement in 2004, many feared large migration flows from new to the old member states. The potential increase in competition on the labour market and for welfare benefits seemed particularly dreadful. That is why Belgium and other old EU member states decided to restrict access to labour markets, before lifting these restrictions gradually. In this publication from IZA, the authors study the evolution of East European workers’ migration, its causes and effects in the new member states. The interested reader will also find some considerations about the crisis’ impact on these migration flows.