In this chapter, the authors focus on one of the most striking innovations in the field of quality assessment: comparative indicators which, since the end of the 2000s, have been integrated into the certification procedure and made public at national level. They deconstruct the managerial innovation in order to analyze its effects in healthcare institutions. The authors outline the context of the emergence of these systems from the end of the 1990s and the issues they raise. They explain the theoretical question of the relationship between management tools and rationalization dynamics in professional organizations, while showing how they have worked on it in their empirical approach. The formalization, standardization and monitoring of activities, through writing and evaluation devices, are classic aspects of professional rationalization approaches. The study of the local effects of quality evaluation instruments allows to defend the thesis of a professional dynamic of hospital transformation.