The Department of Homeland Security’s (DHS’s) Exercise and Evaluation Program defines a red team as a “group of subject matter experts with various appropriate disciplinary backgrounds, that provides an independent peer review of plans and processes, acts as a devil’s advocate, and knowledgably role-plays the enemy using a controlled, realistic, interactive process during operations planning, training, and exercising.” Red teaming techniques are identified as a major initiative in intelligence work by the National Strategy for Homeland Security. Law enforcement agencies are encouraged to use the training technique of red teaming to critically examine the weaknesses, vulnerabilities, and limitations of counterterrorism measures. While red teams are effective for evaluating counterterrorism measures, they do not evaluate the likelihood that a particular target will be attacked. Red teaming can involve a variety of activities, including peer reviews of specific counterterrorism policies, known as analytical red teaming, and field-level exercises, known as physical red teaming. Analytical red teams take the role of the enemy to identify vulnerabilities in plans and policies while physical red teams actually act out known terrorist tactics and techniques to allow for interactive adversity. The methodology for using red teaming is described and involves the development of an action-reaction-counteraction scenario and a safety plan to deal with the increased risks inherent in red teaming exercises. Finally, the benefits and limitations of red teaming are identified as well as the impediments to effective red teaming, which include organizationally imposed restraints and poor scenario planning. Figures, footnotes