This report is a summary of a WERF/NOWRA workshop on Research Needs in Decentralized Wastewater, Stormwater, and Related Fields held on March 14-15, 2007 in Baltimore, MD. The purpose of the workshop was to build future visions, identify research gaps, gain guidance on promising avenues for investment, and begin collaboration discussions within the U.S. and the global community. Participants included U.S. and international professionals and policymakers in decentralized wastewater, stormwater, and related fields. The report includes a literature review which provides an overview of some of the research completed since 2002 related to decentralized wastewater ES&E priorities and to summarize current research in ES&E related to decentralized stormwater (Appendix G).