In 2002, the King County Water and Land Resources Division (WLRD) began conducting a baseline study to assess whether resident benthic macroinvertebrate communities can be used to assess environmental conditions in King County watercourses, and thereby provide a practical tool for monitoring changes in aquatic ecosystem health. EVS Consultants previously completed an analysis of WLRD’s 2002 benthic macroinvertebrate data, and this report presents the results of our analysis of the 2003 data. The focus of this report is the use of the Benthic Index of Biotic Integrity (B-IBI). The B-IBI provides a useful tool for monitoring ecosystem health in King County streams, providing scores that closely parallel the degree of urbanization in the sampled watersheds.