Biota represent the health of aquatic ecosystems, both good and bad, and can show the effects of most human activities on water bodies. Bioassessment of inland waters has gained momentum as managers, the public, and legislators have come to understand the importance of maintaining healthy aquatic biota for sustainable water use. The potential value of biota as indicators of the condition of water bodies has been known since the late 1800s but it is only since the 1980s that real momentum in bioassessment has been seen. Fish, attached algae, floating algae, floating and rooted plants, and invertebrates are all commonly used for bioassessment with emphasis on some different groups in lakes, wetlands, and rivers. Bioassessment is now firmly established from local to national and multinational scales.