Effects of anthropogenic stream degradation on fish assemblages in coastal plain streams of Maryland were investigated by using data from 1989–1993. Fish assemblages, stream physical habitat, and water quality were assessed concurrently at 69 sites. Through the use of habitat and water quality information, two groups were selected from the data set to represent least-impacted streams (N= 16) and most-impacted streams (N= 22). Impacts ranged from agricultural activities involving channelization and riparian destruction to altered hydrologic regime and channel modification related to urban development. Differences in fish assemblages between the two groups indicated that the degraded streams were less diverse and were dominated by a few tolerant taxa, whereas higher-quality sites were characterized by a more balanced assemblage structure and trophic composition, as well as by higher indigenous cyprinid richness and abundance. Various metrics, based on assemblage structure and function under a guild approach, were tested for differences between the high- and low-quality stream groups. The metrics that exhibited the greatest discrimination between groups reflected greater diversity and abundance, a balanced trophic structure, and lower abundance of species considered tolerant to environmental degradation. The most effective metrics included the number of intolerant species present, the number of shiner species, the proportion of silt-intolerant spawners in the assemblage, the proportion of tolerant fishes, and the proportion of insectivorous cyprinids. The metrics that demonstrated ability to discriminate high- and low-quality streams are proposed for development into biological indicators for this region.