-The Piscine Stream Community Estimation System (PiSCES) provides users with a reasonable fish community for any stream reach in the conterminous United States. PiSCES utilizes distributional information obtained from Nature Serve, the USGS, and the Peterson Field Guide to Freshwater Fishes of North America for over 1,000 native and non-native freshwater fish species. In addition to these geographic distributions, users of PiSCES can filter potential fish assemblages based on species rarity, stream size preferences (as measured by mean stream width), and genera-specific occurrence envelopes for a variety of physicochemical stream properties (pH, conductivity, turbidity, dissolved oxygen, watershed area, mean width, depth, and slope). For a user-specified total number of fishes in the stream reach, PiSCES will create an abundance distribution for the posited community using a size spectrum approach that relates abundance to maximum body size. The PiSCES interface allows users to readily access its database to see ancillary characteristics of each species, such as habitat preferences (e.g., if the species prefers riffles, runs, or pools, sand or gravel substrate, etc.) and HUC-based distribution maps. PiSCES has been used in conjunction with an integrated environmental modeling system to simulate dynamics of stream fish communities in the Coal River, WV watershed.