This publication provides guidance on the planning and organization of nuclear security systems and measures for the detection of criminal or intentional unauthorized acts involving nuclear and other radioactive material out of regulatory control (the detection architecture, as described in IAEA Nuclear Security Series No. 21) and for the response to potential nuclear security events (the response framework). The guidance includes processes for reviewing the adequacy of existing nuclear security systems and measures, identifying gaps in capabilities and resources, and designing new systems and measures to address identified gaps.