Damage to or destruction of the nation's water supply and water quality infrastructure by terrorist attack could disrupt the delivery of vital human services in this country, threatening public health and the environment, or possibly causing loss of life. Interest in such problems has increased greatly since the September 11, 2001, terrorist attacks in New York City and at the Pentagon. Across the country, water infrastructure systems extend over vast areas, and ownership and operation responsibility are both public and private but are overwhelmingly non-federal. Since the attacks, federal dam operators and water and wastewater utilities have been under heightened security conditions and are evaluating security plans and measures. There are no federal standards or agreedupon industry best practices within the water infrastructure sector to govern readiness, response to security incidents, and recovery. Efforts to develop protocols and tools are ongoing since the 2001 terrorist attacks. This report presents an overview of this large and diverse sector, describes security-related actions by the government and private sector since September 11, and discusses additional policy issues and responses, including congressional interest. Policymakers are considering a number of initiatives, including enhanced physical security, better communication and coordination, and research. A key issue is how additional protections and resources directed at public and private sector priorities will be funded. In response, since FY2002 Congress has provided $740 million in appropriations for security at water infrastructure facilities (to assess and protect federal facilities and support vulnerability assessments by non-federal facilities) and passed a bill requiring drinking water utilities to conduct security vulnerability assessments (P.L. 107-188). When Congress created the Department of Homeland Security (DHS) in 2002 (P.L. 107-297), it gave DHS responsibilities to coordinate information to secure the nation's critical infrastructure, including the water sector. Under Homeland Security Presidential Directive-7, the Environmental Protection Agency (EPA) is the lead federal agency for protecting drinking water and wastewater utility systems. Recent congressional interest has focused on bills concerning security of wastewater utilities. In the 109th Congress, the Senate Environment and Public Works Committee has approved legislation to encourage wastewater treatment works to conduct vulnerability assessments and develop site security plans (S. 2781). Continuing attention to these issues in the 109th Congress is possible, along with interest in how the federal government coordinates its own activities and communicates policies and information to the water infrastructure sector. This report will be updated as warranted.