This book provides an overview as well as the latest research on currency unions - geographical areas throughout which a single currency circulates as the medium of exchange. The issues discussed are central to debates on economic and monetary union in Europe, and the future of Eastern Europe. In addition to a specially written survey chapter by the editors, it contains previously unpublished contributions by leading researchers in the field, discussing real and potential currency unions in the United States, the former Soviet Union, Europe, and Africa.