This report documents and summarizes physical, chemical, and biological data collected during 1999–2004 in a study of the effects of urbanization on stream ecosystems in nine metropolitan areas: Atlanta, Birmingham, Boston, Dallas-Fort Worth, Denver, Milwaukee-Green Bay, Portland, Raleigh, and Salt Lake City. The purpose of this study was to examine differences in biological, chemical, and physical characteristics of streams across a gradient of urban-development intensity. This report describes methods of data collection and processing for streamflow variability, stream temperature, instream chemistry, instream aquatic habitat, and algal, macroinvertebrate, and fish communities. The data summaries prepared for analytical use are presented in downloadable data tables.