[en] By international agreements, the movement of all radioactive materials within and between States should be subject to high standards of regulatory, administrative, safety and engineering controls to ensure that such movements are conducted in a safe and secure manner. In the case of nuclear materials, there are additional requirements for physical protection and accountability to ensure against threats of nuclear proliferation and to safeguard against any attempts at diversion. The results of the terrorist attacks of September 2001 emphasized the requirement for enhanced control and security of nuclear and radioactive materials. In this regard, measures are being taken to increase the global levels of physical protection and security for nuclear materials. Experience in many parts of the world continues to prove that movements of radioactive materials outside of the regulatory and legal frameworks continue to occur. Such movements may be either deliberate or inadvertent. Deliberate, illegal movements of radioactive materials, including nuclear material, for terrorist, political or illegal profit is generally understood to be illicit trafficking. The more common movements outside of regulatory control are inadvertent in nature. An example of an inadvertent movement might be the transport of steel contaminated by a melted radioactive source that was lost from proper controls. Such a shipment may present health and safety threats to the personnel involved as well as to the general public. States have the responsibility for combating illicit trafficking and inadvertent movements of radioactive materials. The IAEA co-operates with Member States and other international organizations in joint efforts to prevent incidents of illicit trafficking and inadvertent movements and to harmonize policies and measures by the provision of relevant advice through technical assistance and documents. As an example, the IAEA and the World Customs Organization (WCO) maintain a Memorandum of Understanding (MOU) (1998) to promote co-operation at the international level in order to improve the control of radioactive materials. At the time of the drafting of this report, a similar MOU between the IAEA and the International Criminal Police Organization (INTERPOL) is pending. There are a number of measures that must be undertaken by States to combat the illicit trafficking and inadvertent movements of radioactive materials. These measures are, generally, shared between the regulatory and law enforcement agencies as part of a State's national arrangements. One of these measures is monitoring for radioactive materials at borders. This Technical Document (TECDOC) provides information to front-line officers on response to events involving the detection of inadvertent movement or illicit trafficking of radioactive materials. The emphasis in this publication is on operational and tactical response measures. These may entail a multi-agency response, particularly at the tactical level. Detailed scientific information has been kept to a minimum as it is recognized that the majority of law enforcement personnel will not have the background necessary to use such information effectively. The prime objective of this TECDOC is to provide Member States with practical information for use by emergency response and law enforcement personnel involved in dealing with incidents of inadvertent movement or illicit trafficking of radioactive materials. The purpose of the response is to regain control of the relevant radioactive materials so that the risk of harm to people and the environment is mitigated. This information is aimed primarily at police, customs and other law enforcement officers who may become involved in incidents concerning inadvertent movement or illicit trafficking of radioactive materials. Effective inter-agency co-operation can only be achieved if personnel who are not normally involved with radiological emergencies are aware of the issues associated with radiation protection that have to be considered in such cases. It is also likely to be of use to radiation protection specialists who are part of the planned technical response to such incidents and who need to understand the statutory and forensic interests of their law enforcement colleagues