The Maastricht Treaty set the stage for a monetary union in Europe, but the transition period before full union could be rocky. National monetary policies could cause problems with exchange rates and balance of payments. The treaty didn't provide clear solutions for this transition. The European Monetary System (EMS) was the framework for monetary cooperation before the treaty, and it hasn't changed much since. The success of the monetary union will depend on how well the old EMS can handle the new circumstances, like freer movement of capital. A currency crisis in the early 1990s showed that the EMS might struggle to maintain stability.