Whereas much has been said about the reasons behind Poland’s path to the euro, it has been less common to consider the potential interest in eurozone enlargement among its current members, such as Germany. This article offers an overview of possible, mainly economic, rationales that might explain the engagement of incumbents in expanding the common currency area. Abandoning traditional cost-benefit analyses and adopting other frameworks, such as improved competitiveness, cooperation processes or group interactions (games) might be alternative methods to analyse such interests.