The end of the Cold War crucially changed the way in which the world is organised and brought an end to what is referred to as the “old” regionalism. A trend towards some form of “new” regionalism has thus been observed during the 1990s. The objective of this thesis is therefore, firstly, to outline the characteristics of the new regionalism in order to examine to what extent the phenomenon is reflected in the reality of regional organisations, and, secondly, to establish which model of co-operation the same organisations can be said to follow. Following this idea, a comparative case study is performed with the selected cases of NAFTA and MERCOSUR, on which a theoretical model for analysis is applied in order to establish whether theories of International Relations, in this case Liberalism and Realism, can explain the emergence and existence of both organisations.

Results show that NAFTA is less inclined to show signs of the trend towards the new regionalism than MERCOSUR does, and that NAFTA to a larger extent follows a realist model of co-operation, while MERCOSUR follows a more liberal model of co-operation.