Purpose – This paper seeks to investigate the work performed by French Cour des comptes magistrates as part of performance audits. The research objective is to understand who the magistrates are, what they do, how they do what they do, how they perceive their role, what authority they feel they can claim, and how, through performance audits, they try to influence the way the organisations they visit are run. Design/methodology/approach – In addition to 35 interviews conducted with Court magistrates (based on a semi-structured interview questionnaire) and non-participant observation, public documentation was analysed. To understand how magistrates perform their tasks at the Court, basic theories on influence processes and theories on decision making developed by Herbert A. Simon were applied. Findings – After exploring the universe in which magistrates of the French Cour des comptes operate, it appears that their undertaking of performance audits has engendered a host of competing visions: the transition to modernity has to occur. The Court presents itself officially as a supreme audit institution but it acts as a grand corps de l'État (senior branch of the Civil Service). Magistrates come to the Court of their own accord and make every effort to avoid being viewed as control professionals. The Court openly positions itself as a “judge of management”, wishing to impose its jurisdictional authority on activities that are essentially professional in character. A migration from traditional roles is observed: the role of the Court as a critic of the Administration has been sidelined. In addition, the magistrates claim to be judges when they are in the ambit of the Court, but shed this role for that of “catalysts of change” when they interact with representatives of the organisations audited. Research limitations/implications – The research is based on a detailed analysis of a specific context. This may limit the wider applicability of the findings. However, the data gathered from the French experience could be useful for other supreme audit institutions (SAIs) whose status is equivalent to that of the Court, or whose mandate has expanded in the past decade. Originality/value – This study lifts the veil on the performance audit practice at one of the numerous supreme audit institutions. In addition, the French context has received scant attention from researchers.