While an extensive (US) literature stresses the importance of procedural rules in the evolution of parliaments as well as in the legislative process, very few studies have focused on the European Parliament rules. As a result, the role played by the organization of parliamentary work in this evolution remains understudied. Apparently however, the EP’s trajectory was significantly influenced by its rules of procedure, which have allowed the assembly to optimize its competency and internalize reforms established by the treaties. This paper aims to contribute to the theorization of the EP’s institutional dynamics in light of the North-American theories. It examines the challenges faced by the EP due to the rationalization of its deliberation and the consequences of the procedural changes for the institution, its members and its public image. On the basis of a qualitative analysis of the revisions of the EP rules of procedure from April 1979 to January 2017, we will show that institutional efficiency has become an objective in itself, taking precedence over MEPs’ freedom of action. The various reforms have strengthened ‘democracy through parliament’ at the expense of ‘democracy in parliament’, which could have tremendous consequences for the EP’s image among public opinion.< Leer menos