This paper has focused on the value of exchange rate unions for particular groups of countries and on those characteristics that are likely to make a monetary union desirable and viable. The present situation facing industrial countries is one of high, and increasing, international financial integration; in those circumstances, some loss of monetary independence is inevitable. The fundamental question implied by membership in a currency union is whether the loss of monetary independence is likely to be more than compensated for by reductions in transactions costs and in exchange rate uncertainty, by superior inflation performance, and by the credibility added to the global purpose of economic and policy union. This question is currently most relevant to the EC, where moves toward currency union are part of a general trend toward greater economic and political integration. However, it is also relevant for other potential and existing currency unions, as well as for the entire membership of the IMF, as regional currency unions are likely to affect the functioning of the international monetary system.