The article describes the specifics of the organization of the Brotherhood of the Blackheads, which was an association of merchants in the medieval Livonia. The main attention is paid to the internal arrangement as a selforganizing structure. The accent was shifted from economic history to a reflection of some aspects of the inner life and management of the Blackheads’ brotherhood. A branch of this corporation in Reval (modern Tallinn) was chosen as an example. Attention to the functioning of the internal structure within the association allows establishing general models for the development of social mobility, which in turn allows the addition of an understanding of the system of social hierarchies in the medieval city and a guilds’ role in the urban community. In the process of research, not only the latest research on this topic was involved, but also the materials of the Tallinn City archive.