In May 2004, eight countries of Central and Eastern Europe were admitted to the European Union (EU). In January 2007, Romania and Bulgaria, and in July 2013, Croatia were admitted to the EU. These new EU member states (NMS) are not given the right to opt out as the UK and Denmark have, and they are obligated to adopt the Euro. Among eleven new member states, five countries adopted the euro: first Slovenia (2007), followed by Slovakia (2009), Estonia (2011), Latvia (2014) and Lithuania (2015). This book considers the problems of the Eurozone Enlargement by reviewing the experiences of NMS which have adopted the Euro and considering prospects of NMS which have not yet adopted the Euro. The book is divided into two parts. Part One mainly deals with NMS which have already adopted the Euro and takes a closer look at their experiences. Chapter One explains the evolution and the current situation of the EMU in order to get an overall picture of the Eurozone. Chapter Two discusses Slovenia''s experiences of the euro adoption and its lessons. Chapter Three discusses the experiences of Slovakia which adopted the euro in January 2009 exhibiting, in contrast to Slovenia, a favorable performance. Although having seriously suffered from the 2008 global financial crisis, the Baltic States have recovered quickly. Chapter Four discusses what kind of lessons could be drawn from the experiences of the Eurozone NMS, focusing on Latvia and Slovakia. Part Two deals with the NMS which have not adopted the Euro yet, but are expected to. Chapter Five not only discusses Poland''s prospects for Euro adoption but also serves as an introduction to Part Two as a whole. It deals with not only the criteria which should be met by prospective Eurozone member NMS (i.e. explicit Maastricht convergence criteria), but also the criteria of implicit and substantial convergence (i.e. The Czech Republic and Slovakia maintaining close economic relations in spite of their separation in 1993). Slovakia adopted the Euro in January 2009 while the Czech Republic has not yet adopted it. Chapter Six discusses the current situation and challenges of the Czech Republic in comparison with Slovakia. Chapter Seven analyses the Hungarian situation both from a perspective of a comparison with other CEE countries, and from a historical perspective of its long-term transition process. Chapter Eight considers challenges facing Croatia, which has an industrial structure quite similar to Greece. Among prospective Eurozone member states, Romania is the only one country which has its target date for Euro-adoption of January 1, 2019. Chapter Nine considers Romania''s current situation and its challenges. Chapter Ten discusses challenges facing Bulgaria, which has maintained the currency board system. Although the Western Balkan countries are not discussed directly, this book has important implications for them. The authors of the book include five economists from Central Eastern Europe and three economists from Japan. This book is a product of international academic cooperation between Europe and Asia.