Fish communities from 22 reaches at 18 stations in the Ozark Plateaus were sampled in 1993, 1994, and 1995. The 18 stations were chosen to represent selected combinations of major environmental factors (geology/physiographic area, land use, and basin size). Additional physical, chemical, and biological factors also were measured for each of the 22 reaches and the influence of these factors upon the fish communities was investigated. Fish community samples collected at the 22 reaches identified differences in these communities that can be attributed to differences in land use and related water-quality and habitat characteristics. Communities from agriculture reaches tended to have more species, increased relative abundance of stonerollers and members of the sucker family, and decreased relative abundance of members of the sunfish and darter families. Several groups of environmental factors (concentrations of nutrients, organic carbon, suspended sediment, and dissolved oxygen; measures related to ionic strength; measures related to riparian vegetation; measures related to substrate; and measures related to stream size) appear to be related to land-use differences and fish community differences. Three multivariate analysis techniques (two ordination techniques and a classification technique) yielded similar results when applied to the fish community data. Fish communities from reaches with more similar land use in their basins and with similar drainage areas generally were grouped closer together in the analysis. Water quality, substrate, stream morphology, and riparian measures appear to be affecting fish communities at these reaches. The relations between land use, stream size, and fish communities have implications for waterquality assessments of Ozark streams. Compared to other parts of the United States, many fish species live in the Ozark Plateaus. At least 19 of these species are endemic to the Ozarks area. Many of these species are intolerant of habitat or waterchemistry degradation. This characteristic makes fish a useful tool for assessing water-chemistry and other habitat conditions of streams. Several environmental factors can contribute to differences in fish communities. Elevated nutrient concentrations and greater canopy angles can increase periphyton production. Greater canopy angles can raise water temperatures and, if they reflect less woody vegetation along the banks of streams, can be associated with greater streambank erosion. Elevated suspended sediment concentrations and finer and more embedded substrates can reduce benthic macroinvertebrate populations, decrease spawning success of many fish species, and decrease protection of benthic fish from water velocities and predators.