I: The State of the Art.- 1. The optimality criteria.- 2. Conditions for existence of a monetary union.- 3. The change in structural parameters.- 4. The underlying models.- 5. The game theoretical approach.- Conclusions.- II: An IS-LM-AS Model for a “Small” Exchange Rate Union.- 1. The model.- 2. The efficacy of monetary policy.- 3. The efficacy of fiscal policy.- 4. The model, the change in structural parameters and the optimality and existence conditions issues.- Conclusions.- III: Monetary and Fiscal Policy in a “Small” Exchange Rate Union — a Strategic Analysis.- 1. Monetary policy: the system of interdependence and the authorities’ utility functions.- 2. Monetary policy: the Nash, cooperative, Stackelberg and monetary union solutions.- 3. Concluding remarks on monetary policy coordination.- 4. Fiscal policy: the system of interdependence and the authorities’ utility functions.- 5. Fiscal policy: the Nash, cooperative and Stackelberg solutions.- 6. Concluding remarks on fiscal policy coordination.- IV: An IS-LM-AS Model for a “Big” Exchange Rate Union.- 1. The model and its formal representation.- 2. Symmetry assumptions and other simplifications introduced for computational reasons.- 3. The efficacy of monetary policy: the short run.- 4. The efficacy of monetary policy: the medium run.- 5. The efficacy of monetary policy: the long run.- 6. The efficacy of monetary policy: the case of fixed exchange rates between the union and the rest of the world.- 7. The efficacy of fiscal policy: the short run.- 8. The efficacy of fiscal policy: the medium run.- 9. The efficacy of fiscal policy: the long run.- 10. The efficacy of fiscal policy: the case of fixed exchange rates towards the rest of the world.- Conclusions.- V: Monetary and Fiscal Policy in a“Big” Exchange Rate Union — a Strategic Analysis.- 1. Monetary policy: the system of interdependence and the authorities’ utility functions.- 2. Monetary policy: the Nash, cooperative and Stackelberg solutions.- 3. Conclusions on monetary policy.- 4. Fiscal policy: the system of interdependence and the authorities’ utility functions.- 5. Fiscal policy: the Nash, cooperative and Stackelberg solutions.- 6. Conclusions on fiscal policy.- Conclusions.