The United States Environmental Protection Agency (EPA) is responsible for assessing the extent of environmental contamination and human health consequences in the event of a radiological incident such as a terrorist incident involving radioactive materials. Although the EPA will be mainly involved in the intermediate and recovery phases of an incident response, there also may be involvement in some activities in the early phase. This book describes project method validation guidance that a radioanalytical laboratory should comply with in order to validate methods used to process samples submitted during a radiological or nuclear incident, such as that caused by a terrorist attack. These responsibilities include response and recovery actions to detect and identify radioactive substances, and to co-ordinate federal radiological monitoring and assessment activities.