A recently proposed index of biotic integrity (IBI), which applies features of indigenous fish communities to assess watershed and stream quality, is based on the assumption that community features change consistently with stream degradation. In this study, the IBI was modified for and applied to small coolwater streams in the Appalachian Plateau region of West Virginia. Changes in fish community variables proposed for the IBI were tested in seven similar streams exhibiting a wide range of stream degradation due to sewage, mining, and urbanization. A consistent response with increasing stream degradation was found for the following variables: Total number of species, proportion of individuals as creek chubs Semotilus atromaculatus, species richness and composition of darters (Percidae), number of fish in sample, and proportion of fish with disease or anomalies. Proportions of omnivores, insectivorous cyprinids, and herbivore-detritivores yielded inconsistent results due to confounding interactions with species tolerance, whereas alternative trophic metrics, the proportions of specialist insectivores and generalist feeders, produced consistent trends with increasing stream degradation. A modified IBI, based on six fish community attributes, exhibited close agreement with independent rankings of stream degradation.