The Water Contaminant Information Tool (WCIT) is a secure, on-line database that provides current, reliable information on chemical, biological, and radiological contaminants of concern for water security. The WCIT database assists in planning for and responding to drinking water and wastewater (water) contamination threats and incidents. As a planning tool, WCIT supports vulnerability assessments, emergency response plans, and site-specific response guidelines. As a response tool, WCIT provides contaminant data to help responders (including utilities) make appropriate response decisions. WCIT also helps EPA to identify gaps in contaminant data, which will, in turn, help inform future research efforts.