The events of 11 September 2001 focused heightened attention on the security status of the nation's drinking water supplies and the vulnerability of this critical infrastructure sector to attack. As discussed in this book, Congress since has enacted security requirements for public water systems and has provided funding for vulnerability assessments, emergency planning, and drinking water research. The Environmental Protection Agency (EPA), the lead federal agency for the water sector, has worked with water utilities, state and local governments, and federal agencies to improve the drinking water security. Thus, although EPA, states, localities, and water utilities have taken steps to address security concerns, the security of the nation's water supplies continues to attract congressional attention. This book reviews governmental and water utility efforts to improve drinking water security.