The Emergency Consequence Assessment Tool (ECAT) is an interactive web-based software tool. ECAT is designed to meet the challenge of assessing health risks and determining what actions need to be taken during a crisis caused by a terrorist attack or natural disaster. ECAT provides instant access to key information and allows its users to conduct rapid analyses. The tool also provides a holistic approach to rapid risk assessment by integrating critical information across many diverse scientific disciplines and is a useful training tool. ECAT allows its users to conduct health risk assessment, risk management, and risk communication. It allows users not only to define the health threats, but also to determine what actions need to be taken to protect the public and first responders, and how best to communicate this information to the public. It evaluates the risks from chemical and biological agents in multiple environments, such as indoors, outdoors and from water contact, including ingestion, inhalation, and dermal exposure. Further, ECAT has the potential to quantify risks to different human subpopulations.