Book excerpt: The purpose of this document is to establish performance requirements and testing methods for active walk-through metal detectors used to find metal weapons and/or metal contraband carried on a person and/or concealed by a nonmetal object. The Office of Law Enforcement Standards (OLES) of the National Institute of Standards and Technology (NIST) provides technical support to the National Institute of Justice (NIJ) program to support law enforcement and criminal justice in the United States. OLES's function is to develop standards and conduct research that will assist law enforcement and criminal justice agencies. OLES is: (1) subjecting existing equipment to laboratory testing and evaluation, and (2) conducting research leading to the development of several series of documents, including national standards, user guides, and technical reports. This document covers research conducted by OLES under the sponsorship of NIJ. Additional reports as well as other documents are being issued under the OLES program in the areas of protective clothing and equipment, communications systems, emergency equipment, investigative aids, security systems, vehicles, weapons, and analytical techniques and standard reference materials used by the forensic community.