This paper examines, from a comparative perspective, access to information by institutions responsible for the external oversight of intelligence and security services. It addresses both the legal and institutional frameworks relating to access, and also considers the protection of classified or otherwise confidential information by oversight bodies. The paper was written for the Open Society Foundations – Justice Initiative’s (OSF-JI) project on National Security and the Right to Information. It provides analysis to support parts of the Global Principles on National Security and the Right to Information, the development of which is being coordinated by the OSF-JI.