Accession to the Economic and Monetary Union is one of the most important steps in Hungary's European integration, which will entail abandoning the national currency and adopting the euro as domestic legal tender. For Hungary as a new member state in the EU, introduction of the euro will not be an option but an obligation. Nevertheless, new EU members will have some leeway to set the date of adopting the euro1. Therefore, it is useful to analyse the likely costs and benefits of joining the euro area for Hungary and to define the choice of medium-term economic policy strategy in the light of the results of this analysis. The National Bank of Hungary would like to contribute to the formulation of an economic policy strategy by issuing this volume, which contains a cost-benefit analysis of the likely effects of the country's joining the euro area. This analysis is confined strictly to the economic benefits and costs of introducing the euro and is not intended to examine its other possible impacts, including, for example, the implications for politics and national security. Adopting the euro will likely have a permanent impact on Hungarian economic growth. This impact will become evident through numerous channels. Bank staff have attempted to quantify and sum up the extent of this impact transmitted through the various channels. The findings of this analysis suggest that the introduction of the euro will bring about significant net gains in growth. However, welfare is influenced not only by the level and rate of GDP growth, but their stability as well. A widely fluctuating national income will produce lower welfare than a more stable one, even if on average the two income levels are identical. For this reason, it is important to examine whether joining the euro area will increase or mitigate the volatility of business cycles. In other words, the key question is whether Hungary and the euro area form an optimum currency area, that is whether the monetary policy of the euro area is capable of adequately substituting independent Hungarian monetary policy in smoothing out cyclical fluctuations. In the findings of this analysis, the euro area seems to be in most respects at least as optimal a currency area for Hungary as for less developed euro area member countries.