The worldwide need for fresh sources of drinking water continues to outstrip supply while the resources necessary to develop new supply remain limited. The best solution to this dilemma is the coordination of research efforts on an international basis. The Desalination and Water Purification Roadmap presents a summary of the water supply challenges facing the United States, and suggests areas of research and development that may lead to technological solutions to these challenges. These solutions have international application at the same time that innovation is occurring internationally. This Roadmap is a living document-updates to the Roadmap may be made on a regular basis to ensure that it remains current and relevant. The Roadmap is also complemented by a series of additional documents, created as a result of meetings to be held, focused on: Defining discrete research projects and priorities based on the information contained within this Roadmap; Identifying regulatory issues related to the implementation of desalination and water purification technologies, and developing potential solutions where conflicts are found; Identifying, evaluating, and quantifying the impaired water resources to better assess the impact that desalination and water purification technologies may have on water supplies; Generating plans to accelerate the commercialization of desalination and water purification technologies developed as a result of this Roadmap. This Roadmap cannot exist in a vacuum-technology development must be undertaken with the context of the product's end-use in mind. The goal of this process is to: Develop a consensus and direction to guide investments for the creation of new water purification technologies; Identify the roles that various sectors of the economy (e.g., national government agencies, the private sector, educational and non-profit organizations) can play in the creation of new water purification technologies; and Develop an expert group to review alternative water purification technologies. Toward these ends, we are now joined by a number of national and international organizations, each of which is contributing its own resources to a common end. This end includes assistance in developing novel water treatment technologies as well as improving and sharpening the roadmap itself.