The Freshwater Biological Traits Database currently contains traits data for 3,857 North American macroinvertebrate taxa and includes habitat, life history, mobility, morphology, and ecological trait data. Species traits are the characteristics that explain an organisms relationship to the surrounding environment, including how it grows, feeds and moves. The traits data were compiled for a project on climate change effects on river and stream ecosystems that was conducted by the Global Change Research Program in the National Center for Environmental Assessment in the U.S. EPA Office of Research and Development. The traits data were gathered from multiple sources. Data gathering efforts focused on data that were published or well-documented, available, appropriate for the regions being studied, in a standardized format that could be analyzed or easily converted to a format that could be analyzed, and ecologically relevant to the gradients being considered. The database has been posted online to facilitate further research. This is intended to be a living database, and researchers are encouraged to contribute data and provide suggestions or feedback on how the database can be expanded and improved upon in the future.