Diplomarbeit aus dem Jahr 2006 im Fachbereich VWL - Geldtheorie, Geldpolitik, Note: 1,7, Universität Ulm, 341 Quellen im Literaturverzeichnis, Sprache: Deutsch, Abstract: With the adoption of the EURO among some of the new countries in the European Union during the next few years, heterogenity of the European market will increase endangering economic stability. Most authors expect a decrease in optimality conditions of the eurozone referring to the theory of optimum currency areas. This diploma thesis tries to answer the question, whether the eurozone (EU 12), or the eurozone including Denmark, Sweden and the United Kingdom (EU 15), or, with respect to the future, an eurozone including the 10 new members of the European Union (EU 25) can be seen as an 'optimum currency area' (OCA). In Part 1, the Theory of Optimum Currency Areas (OCA-theory), starting with the 'founding-father' Robert Mundell in the early 1960ies is discussed critically, in part 2 macroeconomic aspects of the theory of optimum currency areas are presented and in part 3 costs and benefits of European Monetary Unification are discussed. In the main part, 4, the theory of optimum currency areas is applied on the eurozone, focussing on alternative absorptions-mechanisms after asymmetric shocks, macroeconomic structures of the current (and new) members and the level of correlation of business-cycles between the cycles of EMU-12 and those of each acceding country. With positive, high correlations standing for evidence of low risk of shock asymmetry and therefore optimality conditions, the economies of the European Union are analysed. The results show, that some of the new members share similar structures with some 'old' EMU-members, and are therefore 'good' candidates, some other results are less encouraging.