A concept of competition hierarchy among ant species is presented. The hierarchy consists of three main levels, and the species are arranged in the hierarchy on the basis of social organization (mainly forager densities and recruitment efficiencies) of colonies. The concept allows testable predictions on probable and improbable species pairs in local ant species assemblages. Structure of competition hierarchy and positions of a number of North European species in it is reviewed. A schematisized map on minimal distances among nests of species belonging to various levels of the hierarchy is presented. A case study on relations among highest-level, territorial species, is described.