As part of an ongoing Ph.D. project focusing on medieval assembly sites in western Norway, this paper discusses administrative units in the Hardanger district. An improved understanding of the medieval administrative organization, particularly local-level units, is of vital importance for the study of assembly sites. Using Hardanger as a case study, this paper discusses how reconstruction of older administrative units can be attempted by a detailed retrogressive study combining written sources and archaeological material. Although preliminary, the investigations indicate that in some parts of western Norway, among them Hardanger, the administrative structure differed from the general model described for the region. This finding implies a larger degree of heterogeneity in social and political organization within the medieval Norwegian kingdom than hitherto assumed.