Geographical elements are defined by reference to the geographical range of taxa as mapped. In analysing the geographical distributions of the taxa that comprise the flora of a particular territory, it will be seen that the individual distribution maps for each taxon exhibit an areal bias. In very simple terms, for example, some taxa will be confined to the north of the territory, others to the south, east or west, and others again may possess a very general distribution throughout. The traditional method of examining the floristic affinities between geographical areas is the recognition of what are termed floristic units or floristic regions. The average geographical range of species is fairly small and at the world scale these limited ranges may be grouped geographically into regional units or floras which are differentiated on the basis of their distinctive taxa. The chapter is concerned with methods of identifying natural groupings of taxa based on their geographical areas as mapped.