Part of the solution to public sector corruptions lies, generically, in the accomplishment of programmes and managerial functions within a governmental audit organisation and within a public governance network to which such an organisation belongs. While it is generally true that auditing can have a positive effect in reducing corruption, nevertheless such an effect is certainly not intrinsic to auditing. It depends on the way auditing is organised and operated, considering the institutional context in which it is immersed. The presentation will show the preliminary results of an analysis of a case study of an audit programme that has been shown to be effective in reducing corruption, as demonstrated by several empirical studies. The case is the municipality-facing auditing programme carried out by CGU (Controladoria-Geral da União), the audit body that is institutionally part of Brazil’s Federal executive power. By applying the notion of “social mechanism”, Sergio Seabra seeks to open the “black box” to understand what it is about government auditing that explains its effect in reducing corruption. He will argue that the effect of CGU’s programme can be explained by the operation of four social mechanisms, which were activated by the combination of a number of programme design features and context factors. By using the notion of social mechanism, and the causal connections among programme features and programme context factors, we can make a step further in understanding “how” it generated its effect on corruption, in such way that enables practitioners (programme planners) to benefit from the study of prior experience.