Increasing interest and attention are being directed at the relationship between water and energy resources in the United States. To better weigh the trade-off s and take actions to optimize these resources in concert, the Alliance for Water Effi ciency (AWE) and the American Council for an Energy-Effi cient Economy (ACEEE) teamed up to investigate what relevant research and studies exist that can inform these actions. Even a modest inventory can inform choices about eff ective and relevant research investments as a fundamental method for addressing issues and challenges inherent to this relationship.This paper, prepared by GEI Consultants, Inc. on behalf of and in collaboration with AWE and ACEEE, provides the results of an assessment into the status of research on the relationship or “nexus” between the water and energy sectors. Publicly available research papers and studies that met certain criteria were collected and catalogued into a database. These included investigations that addressed the water sector’s impacts on energy resources and the energy sector’s impact on water resources, including development, operations, and end-uses. The compiled research was then assessed to determine the scope of topics investigated, the key results, and possible gaps. Finally, gaps in the research were identifi ed and inventoried. From this information, a roadmap for future research investments is recommended to enhance multi-sector resource management and overall resource effi ciencies. A summary of the major fi ndings from the collected research is provided and is compared to the major policy objectives and issues as identifi ed in the AWE-ACEEE publication, Addressing the Water-Energy Nexus: A Blueprint for Action and Policy Agenda (Blueprint). From this comparison, final recommendations were developed that address additional research needs.