This publication presents detailed concepts and procedures for the preparation, conduct and evaluation of exercises to test relevant nuclear security systems and measures, and provides useful templates and checklists that can be used to assist the exercise development process. The technical guidance provided is targeted at States and their competent authorities to assist them in establishing and sustaining an effective infrastructure to strengthen detection of and response to material out of regulatory control and evaluate the effectiveness of their plans by presenting a structured methodology for the consistent development of exercises.