External audit agencies are an integral part of the system of checks and balances. However, little is known about what explains their effectiveness and what determines their performance. Combining quantitative and qualitative research techniques, the dissertation investigates the political economy of government auditing and budget oversight in emerging economies. Building on earlier findings on the role of political institutions in economic performance, it develops a conceptual framework to assess the effectiveness of external audit agencies. Gathering quantitative data for ten Latin American countries, it develops a performance indicator to assess the links between external auditing and fiscal governance. It then investigates three case studies, Argentina, Brazil and Chile, illustrating the three main models of external auditing. Interestingly, the research reveals a paradox of independence: while external audit agencies must be sufficiently autonomous to be effective and credible, they need to develop efficacious relations with the other components of the system of fiscal control with the necessary powers to enforce accountability on government, in particular parliaments. This research expands knowledge on oversight agencies and opens avenues for further research on the role of parliaments in public budgeting.