Online communities are a topic of increasing academic and practitioner interest. Yet, little is known about the underlying mechanisms of building a firm-hosted online community. Our in-depth single-case study of how the world’s largest miniature model railway exhibition established a vital firm-hosted online community addresses this gap. We identify a process consisting of three key practices – luring, documenting, and moderating – that explains the inherent challenge of building a firm-hosted online community: how to attract and how to keep people engaged with the online community. Presenter: Leona Achtenhagen.