This publication provides comprehensive detailed guidance for States, competent authorities and operators on how to implement the recommendations and implementing guidance of existing IAEA Nuclear Security Series publications for an effective physical protection system (PPS) for nuclear facilities and nuclear materials in use and storage. It provides further technical detail on how to design and evaluate a PPS, with respect to the selection and integration of appropriate, effective physical protection measures (including equipment). The publication is intended to serve as a general reference, pointing users to other complementary guidance on specific topics.