With more than 100 right to information (RTI) laws also called freedom of information or access to information laws now in place globally, the groundwork has been laid to advance more transparent, accountable, and inclusive governance as a pathway to poverty reduction and economic development. This guide explores the historical development of RTI laws, the factors that drive passage and effective implementation of these laws, the operation of the laws, and the impact of these laws in different country contexts and sectors, as well as the challenges of measuring the contribution of RTI laws to development outcomes. Public Access to Information for A Guide to the Effective Implementation of Right to Information Laws is based on two years of research studying how RTI has been implemented in countries in different regions and with varying income levels. The research has aimed to develop a theoretical framework by which to identify the drivers of effective implementation of RTI laws and to support measurement of effective implementation; the outcomes are discussed. This guide grapples with questions such as the What does it mean to have effectively implemented an RTI law? What aspects of a law have to be operational before it can be said to have been effectively implemented? What other factors are most critical to the effective implementation of RTI laws? Why does effective implementation of RTI matter?