The European Monetary Union (EMU) currently finds itself in its deepest crisis. The general confidence in this ambitious European integration project which was apparent in the run-up to the EMU has now given way to considerable skepticism. While the movement towards EMU started after the end of World War II, this paper provides an economic assessment of these developments. However, one has to keep in mind that the process of European integration is not exclusively driven by economic factors. The foundation of EMU was inspired by the so-called theory of optimum currency areas and political authorities put a system in place which led to the formulation of four convergence criteria. However, regarding these criteria, several mistakes were made which at the very least contributed to the prevailing crisis. In particular, the relevance of sovereign debt and national budgets were benignly neglected. Furthermore, planned sanctions for violations have not been imposed. Currently, debt seems to be getting out of hand and the European Central Bank (ECB) remains the last authority which is able to act. This generates additional problems. While the measures taken by the ECB are legally questionable, it generates political dependencies. For the future, several scenarios are possible. The first possibility is that some countries might secede from the EMU, which will lead to problems both for the seceding country and also for the remaining countries of the EMU. As a second option, further steps of integration will have to be made, especially fiscal integration. Right now, it seems as if the second possibility is the preferred option.