This publication provides guidance to States on the development, implementation, maintenance and sustainment of a national framework for managing the response to nuclear security events. Such a framework involves a structure and a set of principles and agreements around which a State can frame its nuclear security response functions, addressing the interfaces which need to exist between responding agencies to ensure effective, coordinated response. By using this Implementing Guide, a State will ensure that it has considered all relevant key issues as it develops its national framework for responding to nuclear security events.