Over the past few decades, transformations at work, such as Robert Castel has analyzed them, and their consequences on the development of professional careers, have drawn attention in political, media and societal spheres. Professional retraining is a transitional phase that questions the place and meaning given to work today. An individual and collective event, it can generate a period of inactivity or unpaid activity that is rarely perceived as an active phase in a career. Professional retraining can be seen as a change of direction and sometimes a change of life, since the changes it entails are accompanied by a decentering that is not only professional but also personal. Although we may speak of "voluntary occupational retraining", not all reconversions fall under this category. Indeed, reconversion is also sometimes “an important and brutal change in the direction of the trajectory, of which both the moment and the outcome were unpredictable”. However, the two characteristics of situations evoked by Michel Grossetti – the greater or lesser predictability of the moment of its occurrence and of the possible outcomes – enable us to understand reconversion as a dynamic process produced by a set of relations which determine the action at a given time. This thematic issue aims at contributing to the understanding of the conversion to the profession of teacher, the place and role of these reconverted teachers in the educational system and the institutional dimension linked to the evolution of the social composition of the teaching staff and teacher training.