The book draws comparison between MERCOSUR and the European Union to explain variation of regionalism and to expose its limits. The project is based on the idea that contemporary examples of regionalism should be evaluated against several propositions of multiple integration theories rather than against a single theory. In order to systematically explain why and how integration outcomes in MERCOSUR differ from those in the EU, the author develops an analytical framework for the comparison of the two blocs. MERCOSUR is compared with the EU by the use of the various criteria of economic interdependence, economic convergence, intra-bloc size and interest asymmetries, cultural diversity and geostrategic motivations, which are identified as the salient parameters of integration theories.