The OECD DAC Handbook on Security System Reform: Supporting Security and Justice provides guidance to operationalise the 2005 DAC Guidelines, Security System Reform and Governance, and closes the gap between policy and practice. It largely follows the external assistance programme cycle and contains valuable tools to help encourage a dialogue on security and justice issues and to support a security system reform (SSR) process through the assessment, design and implementation phases. It also provides new guidance on monitoring, review and evaluation of SSR programmes, and highlights how to ensure greater coherence across the different actors and departments engaged in SSR.