In January 2007 Bulgaria and Romania joined the EU. Thus the EU enlarged itself southeastward. Beyond that there is a problem how to realize the EU accession of West Balkan countries. This paper discusses the prospect of EU accession as “external anchor”, which plays important role in stabilization and economic development of the West Balkans. This paper describes firstly, how Stabilization and Association process was launched and its concrete contents; secondly, present situations of economies of South Eastern Europe (SEE) and thirdly, achievement of each country in the Stabilization and Association process. Finally challenges for the West Balkans is discussed. The reason why the EU became earnest about the Balkan integration in the EU is because it was motivated by political necessity of stabilizing the SEE as a backyard of Europe. The Kosovo war in 1999 was a turning point in the EU's policy toward the SEE. To stabilize the region the EU felt it necessary to give SEE countries more positive prospect, that is, accession to the EU is not so distant future as far as these countries continue to make efforts. According to an optimistic prospect, after the EU accession of Bulgaria and Romania in 2007 Croatia and other countries of the West Balkans will be admitted to the EU one after another by 2015. However, the region still has the following difficult circumstances which do not allow such an optimistic prospect: (a) Structurally very fragile economies; (b) Problems such as weak state, weak rule of law, corruption, organized crime, etc.; (c) Ambiguity of the EU's policy toward the West Balkans; (d) Bosnia and Herzegovina is composed of two Entities, and reconciliation among ethnic groups remains a serious challenge; (e) Kosovo, which has been originally an Autonomous Province of the Republic of Serbia, is now a de facto Protectorate of the UN, and there is a possibility of its independence; (f) Extraditions of war criminals to the ICTY. It may be said that the accession of the West Balkan countries and Turkey would impose heavy burden on the EU, being detrimental to the EU's future competitiveness. There seems to be some truth in a pessimistic view of Welfens who says, “Integration overstretch could be the end of the EU as a prosperous integration club” (Welfens, 2001, p. 94). Instead of enlargement, he recommends the EU to offer attractive association status to Turkey and some countries in the Balkans, and he stresses a necessity for internal effort toward deepening of the integration. However, the EU has already announced, “countries of the West Balkans are potential candidates” (European Council in Feira in June 2000) and “the future of the West Balkans is in the EU” (the European Council in Brussels in March 2003). If the EU attaches more importance to the cohesion of the existing members and discontinue the integration of the West Balkans it would contradict the EU's commitment to countries of the West Balkans and increase dissatisfaction among people in the region, fueling disputes. Therefore, it would be impossible for the EU to withdraw its goal easily. I think that the EU should continuously support economic development of West Balkan countries and promote intraregional cooperation of the region. Bigger assistance should be provided according to efforts made in overcoming parochial nationalism in each country.