On September 11, 2001, 2,792 people were killed in terrorist attacks on the World Trade Center (WTC) in New York City. The number of victims, the condition of their remains, and the duration of the recovery effort made the identification of the victims the most difficult ever undertaken by the forensic community in this country. In response to this need, the National Institute of Justice (NIJ), the research, development, and evaluation agency of the U.S. Department of Justice, brought together a group of experts to provide advice and support throughout the identification effort. Called the Kinship and Data Analysis Panel (KADAP), the group made recommendations on new forensic technologies, tools, policies, and procedures to help identify those who perished in the WTC attack. This report contains the KADAP's "lessons learned," particularly regarding DNA protocols, laboratory techniques, and statistical approaches, in the DNA identification of WTC victims. It is written primarily for the Nation's forensic laboratory directors and other officials who may be responsible for organizing and managing the DNA identification response to a mass fatality incident. Although New York City's mass disaster plan on 9/11 contained lessons learned from the 1993 terrorist bombing of the WTC, it did not contain policies or procedures for identifying mass disaster victims through DNA analysis. Had this been part of the city's plan in 2001, many of the issues that arose after the attacks could have been more quickly resolved. This report discusses the incorporation of DNA identification into a mass fatality disaster plan, including how to: Establish laboratory policies and procedures, including the creation of sample collection documents; Assess the magnitude of an identification effort, and identify and acquire resources to respond; Identify reference and kinship samples; Create a comprehensive laboratory management plan, including technology management and quality assurance; Establish lines of communication between agencies, departments, victims' families, and the press. Designed to augment another NIJ publication, Mass Fatality Incidents: A Guide for Human Forensic Identification, this guide will help the Nation's forensic laboratories-whether called upon to identify victims of a major natural disaster, transportation accident, or terrorist attack-prepare for a mass fatality incident. Although this report does not address every aspect of a mass fatality DNA identification effort, it does stress intentional testing redundancy as a way to monitor a system's effectiveness. The report also discusses how decisions made in the first 48 hours after a mass fatality event shape the scope of the identification effort.