The aim of this study was to inquire into the professional development of French secondary- trainee teachers. The results first showed that learning in the workplace is a multifaceted process including mentoring, learning with experienced colleagues and learning by oneself from classroom teaching. Because trainee teachers tended to cite colleagues more often than mentors, it appears that workplace learning cannot be curtailed to mentoring. The authors argue that the findings of this research have allowed them to claim that there is a relationship between learning modes used for the competencies to be acquired and the content of these competencies.