Extant literature on EMU fails to explain why European countries chose it at the expense of other alternatives that might have been equally promising. I argue in this article that the transition to EMU was facilitated by the factors associated with the paradoxical nature of the successful EMS: adaptational pressure and domestic political conflicts. Adaptational pressure refers to the increasing vulnerability to monetary policy differentials within EMS. The EMS could be successful due to the policy convergence on disinflation. Yet, this convergence rendered member countries more vulnerable to monetary policy differentials within the EMS. The EMU was envisioned as a solution to the rising costs of policy adaptation that was brought about by the successful EMS. Against this backdrop, domestic political actors were sharply divided over the appropriate monetary policies. Those political actors who committed themselves to domestic price stability found in the EMU a vincolo esterno (external tie) to engineer otherwise elusive domestic reform.