States develop detection systems at borders to reduce risks from nuclear and radioactive material. Detection of nuclear security events involving nuclear and other radioactive material out of regulatory control is an important challenge facing States. Timely detection of this material can reduce the risk of it being used in criminal or intentional unauthorized acts. This publication provides guidance for States on planning, implementing and evaluating nuclear security detection systems and measures at State borders. Special consideration is given to designated points of entry and exit and border areas. National competent authorities such as the border guard, customs authorities, national or local law enforcement agencies and regulatory bodies will find this guidance useful for developing, designing, implementing, and sustaining detection systems and measures at State borders.