This paper examines the involvement of supreme audit institutions (SAIs) in auditing the preparedness of governments for implementing the Sustainable Development Goals (SDGs) since 2015. These audits have covered institutional arrangements put in place to implement the SDGs, the mobilization of resources, and monitoring and evaluation frameworks. SDG preparedness audits have produced valuable information that is not necessarily available from other national processes linked with SDG follow-up and review. As such, audit recommendations can be a powerful tool to help governments improve SDG implementation. The paper reflects on the impact that SDG audits have made, and on the challenges and opportunities for SAIs that have engaged in this exercise. While many of these challenges are generic to the work of SAIs, SDG audits also present specific political, institutional and technical problems. Finally, the paper explores questions that this new area of engagement poses for SAIs, including the long-term prospects for institutionalization of SDG audits and the relationship with other accountability mechanisms for the SDGs at the national level. 1. Introduction -- 2. Supreme audit institutions and internationally agreed development programmes -- 3. Current initiatives of supreme audit institutions to audit SDGs -- 4. Impact of SDG audits on transparency and accountability in SDG implementation -- 5. Challenges and opportunities related to SDG audits -- 6. The positioning of supreme audit institutions in national accountability ecosystems around SDG implementation -- Conclusion.