Concerns about the transparency of aid have become more prominent against a recent background of donor commitments to increase aid effectiveness. Innovative approaches to assessing the costs of non-transparent aid and providing more and better information about aid have been developed. This article explores the impact of these aid transparency and accountability initiatives (TAIs). It finds that the links between inputs, outputs and impacts in aid TAIs are often neither articulated nor well-understood. Future attempts to understand the impact and effectiveness of aid TAIs need to take full account of diversity actors, motivations and approaches, to work on the principle of methodological pluralism and to keep in sight the complex and political nature of the aid relationship.