One of the questions in the context of EU-Enlargement is that of East-West Migration. How many people will leave the accession candidate countries and how will this affect the Western European countries? This paper presents a forecast of migration between the accession countries and the EU 15 from 2004 to 2015. The forecast is based on the analysis of migration experiences from the accession of Spain, Greece and Portugal. The results of a multiple regression model show that network effects play an important role. Economic factors have a significant impact only on migration into the European countries but not on emigration. The estimated coefficients are used to forecast future migration. Between 2004 and 2015 about 3.0 million people are expected to migrate temporarily into Western European countries. Permanent migration will be about 1.7 million people. Regarding distribution Germany and Austria are mostly affected by immigration. In terms of emigration quotas Poland will be by far the main source of migrants.