What explains the effectiveness of autonomous audit agencies (AAAs) in emerging economies? AAAs are autonomous state agencies tasked with overseeing government finances. They are a critical component of the system of checks and balances in financial governance. However, in many developing countries, they often fail to fulfill their prescribed roles. This paper models and measures the effectiveness of AAAs in Latin America, developing an index to evaluate their performance, and assesses their reform over time. It examines the cases of Argentina, Brazil and Chile, which illustrate the three models of AAA and three distinct trajectories of reform (or lack thereof).