Transparency has drawn considerable international attention as an umbrella term covering issues relating to the struggle against corruption, the design of more open and participatory government and institutional, corporate, and social agent accountability. It is likewise associated with open data and guaranteed access to public information. However, transparency also has a second important dimension, viz. public disclosure, whereby institutions are required to furnish citizens with public information in their interest. Assessment of both dimensions of transparency poses problems and difficulties. The present article discusses the results of applying the TransPa_BA tool to assess public disclosure in 202 archives and libraries (information units) under the aegis of different government bodies. This tool proposes a series of indicators to measure active disclosure by public libraries and archives in keeping with the provisions of Spanish Act 19/2013 of 9 December on Transparency, Access to Public Information and Good Governance. The indicators and their respective parameters (content, form, reusability, accessibility, dating and updating/validity) establish general outlines enabling these institutions to enhance their transparency by furnishing not only society in general, but also their stakeholders, with information regarding their activities and performance. Accessibility of active public disclosure-related documents was found to be wanting in all but university libraries. As a collective learning tool for information unit managers, TransPa_BA can be used to monitor and gradually improve transparency in libraries and archives.