This Safety Guide is intended to provide recommendations on the establishment of a national strategy for regaining control over orphan radioactive sources and improving control over vulnerable radioactive sources. It provides guidance on how to assess the national situation, and develop and implement a national strategy to achieve these goals. Contents: 1. Introduction; 2. Assessing the problem; 3. Developing the national strategy; 4. Implementing the national strategy; Appendix I: Format and content of a national strategy document; Appendix II: Searching for sources; Annex I: Causes of loss of control over radioactive sources; Annex II: Common problems and possible solutions identified during national strategy missions.