Applications of the IBI concept outside the USA and Canada have retained the same original ecological framework including suites of metrics that represent the four major classes of biological attributes. IBI concepts based on assemblage and community ecology can be applied successfully to the markedly differing fish faunas of all six continents inhabited by freshwater fishes. These results support further development and use of this index as an efficient, quantitative, biological indicator for water resource assessment and monitoring throughout the world. Perhaps the most fundamental requirements for further application of the IBI model is increased knowledge of regional fish faunas (biology, ecology and systematics) together with improved sampling methodologies and monitoring programs. In addition, there is a need to evaluate the indices and metrics against other stressors to assess their general responsiveness to disturbance, and to conduct repeat sampling at the same sites so that the degree of sampling variance can be related to among-site variance.