This report, dated March 2011, presents a series of case studies describing the approaches currently being taken by four water utilities in the United States to assess their vulnerability to climate change. The case studies illustrate different approaches that reflect specific local needs and conditions, existing vulnerabilities, local partnerships, and available information about climate change. Information from these case studies will be useful to water utilities and other members of the water resources community to inform the development of strategies for understanding and responding to climate change. This report was prepared by the National Center for Environmental Assessment's Global Climate Research Staff in the Office of Research and Development.