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 us to anticipate that other such threats are possible. Terrorist threats are targeted not just at individuals, but also at the country's vital institutions and infrastructure, including drinking water and wastewater systems. To combat such threats, it is essential that government agencies, water utilities, state and local water agencies, public health organizations, emergency and follow-up responders, academia, and the private sector from across the country be ready to protect our water infrastructure. These entities are working together to reduce vulnerabilities to terrorism, prevent and prepare for terrorist attacks, minimize public health effects and infrastructure damage, and enhance recovery from any attacks that may occur.