Water - every drop of it - is a precious natural resource that Americans once enjoyed with little thought to potential tampering by terrorists or others. Today, however, U. S. citizens are increasingly aware of threats of harm to our homeland. The terrorist attacks of September 11, 2001, and the delivery of anthrax-contaminated letters later that year have taught all of us to anticipate that threats to water are possible. Terrorist threats are targeted not just at individuals, but also at the country's vital institutions and infrastructure, including the nation's drinking water and wastewater systems. Government, water utilities, state and local water agencies, public health organizations, emergency and follow-up responders, and academia, as well as the private sector from across the country must be ready to protect water infrastructure. These organizations are working together to reduce vulnerabilities to terrorism, prevent and prepare for terrorist attacks, minimize public health impacts and infrastructure damage, and enhance recovery from any attacks that may occur.