Description: The ecoregion framework is a geographic-based tool for organizing environmental data used in water quality monitoring programs. Ecoregions are general abstractions of complex geographic, climatic,hydrologic, and biotic factors that shape the distribution and diversity of flora and fauna in the state. The distribution of fishes and the structure of fish communities are strongly influenced by ecoregions and by stream and river drainage networks. The influence of ecoregions and drainage networks on the distribution of fishes must be accounted for when calibrating biological monitoring tools such as the IBI. Using historical fish collection and distribution data as the basis for the analysis, the 29 level IV ecoregions of Alabama were synthesized into five ichthyoregions through a combination of analytical techniques. The ichthyoregion approach is a preliminary effort to synthesize Alabama's diverse stream networks and ecoregions into a manageable number of natural zoogeographical units for calibrating the fish IBI.