This publication is a revision of IAEA Nuclear Security Series No. 2, Nuclear Forensics Support, which was published in 2006. Since then, there has been substantive expansion and confidence in the application of nuclear forensics globally to effectively counter the threat of nuclear and other radioactive materials out of regulatory control. Most significantly, nuclear forensics has been applied in response to a number of incidents involving the illicit trafficking of highly enriched uranium and plutonium. The essential lessons learned from these experiences are incorporated in the revised publication to update the procedures and methods used in the conduct of a nuclear forensic examination as well as stress the importance of international cooperation.