This report presents and discusses what evidence exists about initiatives to promote transparency among legislators, members of parliament (MPs), and legislative processes and what impact this has had on legislative accountability. In this report we distinguish between two types of accountability: vertical (in which citizens play a direct role in holding the powerful to account) and horizontal (in which legislators hold the executive to account). With regard to vertical accountability, the effects of three policy initiatives are reviewed: i) increased information about MPs including through ICTs; ii) disclosure of MPs’ assets; and iii) disclosure of MPs’ election expenses and funders. Compared to more recent transparency initiatives, such as registers of beneficial ownership information, these initiatives have had a few years to generate some evidence about impact. In relation to horizontal accountability, the impact of transparency on the effectiveness of Public Accounts Committees is reviewed. The choice to focus on this Committee was also made on the basis of available research.