The chapter presents a case study following the activities of super users and local developers during the adoption of a new business application by an accounting firm in Scandinavia (referred to as the Company). The Company launched a program to train super users to help with this process because of the complexity of the new system, a generic, multipurpose application system replacing several older, non-integrated systems. The system, Visma Business (VB), is a comprehensive financial and accounting application delivered as a set of components that need to be configured for domain-specific tasks, depending on the clients the accountants will interact with. The super users and the local end user developer (also called the application coordinator) were asked to take part in this study. We documented their activities empirically and analytically, using interviews to gather data and drawing on aspects of activity theory for the conceptual framework for analysis. Our findings provide insight into end-user development (EUD) activities with VB: what roles were created by the Company, what roles emerged spontaneously during the process, what the various user groups (regular users, super users, and the application coordinator) did, and how EUD was coordinated between super users and the application coordinator. Our findings show that super users fill an important niche as mediators between regular users and local developers and can make a significant contribution to the success of EUD efforts in a nontechnical application domain.