Stream size and zoogeography affected species composition and relative abundance of fish communities more than water-quality effects of land uses among the 21 sites sampled in West Virginia and Virginia. Most commonly-used fish metrics based on counts of species were significantly greater in sites downstream from Kanawha Falls (an important barrier to fish movement) than in sites upstream from Kanawha Falls. Commonly used metrics based on proportions of the fish community belonging to trophic or tolerance guilds were not significantly different upstream and downstream from Kanawha Falls. Variance in some widely used fish metrics was greater among multiple reaches sampled within stream segments than among all sites. Stream size dominated species distribution and site separation along environmental gradients within groups of sites upstream and downstream from Kanawha Falls, according to ordination. Cluster analysis separated the two largest sites from all others, then divided the remaining sites by size and physiography. Similarity of fish species composition, measured using the Jaccard Similarity Coefficient, was less when compared among three contiguous reaches sampled in one stream on consecutive days than among some sites from different streams; within-site similarity decreased with increasing stream size. Cluster analysis grouped all reaches sampled at the same site in the same cluster.