The guide is a functional tool that criminal investigators can carry with them in the field when conducting illegal firearms trafficking investigations. In addition, the guide can assist the law enforcement community in the development of new strategies designed to impact on illegal sources of firearms to criminals, gang offenders, and juveniles. Beginning sections of the guide address the history of the Bureau of Alcohol, Tobacco, and Firearms (ATF) and examine ATF investigative support and illegal firearms trafficking terms. Subsequent sections of the guide consider investigative resources and source information development, illegal firearms trafficking indicators, interdiction procedures and techniques, and the ATF's National Tracing Center. Final sections of the guide cover legal information pertinent to illegal firearms trafficking, investigative flow charts and checklists, financial and insurance fraud investigation and audits, State systems and laws, the firearms import/export process and the sale of firearms to aliens, and State and local law enforcement. ATF forms that can be used by law enforcement agencies in the investigation of illegal firearms are included. Illustrations