This article explores the emergence of nonprofit self-regulation in long-established and emergent nonprofit sectors in Europe. An application of agency, resource dependence, and institutional theories to specific national cases reveals three predominant selfregulation types, compliance, adaptive, and professional models, conditioned on varied market, political, and social antecedents. The compliance system predominates in the Western European cases (Germany, Switzerland, the Netherlands, and Austria), where the nonprofit sector is long established and public regulation of the sector is weak. The adaptive model is evidenced in the United Kingdom, where the nonprofit sector is well established but self-regulation design shifts in response to changes in public regulation and the resource environment. The professional self-regulation type occurs when the nonprofit sector and its legal system both are emergent, as in Poland, with self-regulation emerging to shape philanthropic, civil society, and nonprofit practice. An analysis of the European context more broadly reveals that as self-regulation is emerging across a number of contexts, there is evidence of isomorphism.Globally, the issue of improving nonprofit accountability has garnered much attention. As we discuss in the introduction to this symposium, nonprofit organizations have grown in scope, number, and assets. With this expansion, donors, governments, citizens, clients, and actors internal to the nonprofit sector have shown increased interest in and scrutiny over operations and performance, with a related drive to create or to strengthen existing self-regulation approaches (Bies, 2002; special section of Chicago