The aim of the thesis is to investigate how a number of pedagogical supervisors develope their supervisory competence. In order to meet this objective the following issues were important: What sort of learning takes place among the supervisors?  In what ways have different frameworks and conditions been important for guiding the talks? Can the patterns of conversation be discerned during the sessions and how do these patterns reflect their learning and skills? The thesis presents two studies of educational supervisors and tutor based learning which were carried out with about five years delay. The first study was conducted with twenty newly trained supervisors and a second follow-up study was conducted with ten of the same supervisors.  The analysis of the empirical material of study 1 shows, among others, in which direction the talks evolve during mentor sessions and to what extent they change character to deepen and lead the supervisors to develop new perspectives and ways of looking at their role.  The analysis of the empirical data in study 2 illuminate how each supervisor’s learning progresses by analyzing interviews, conversations and reflections. This study analyzes the supervisors’ levels of reflection, the traditions reflected in the supervisors’ way to lead session conversations, the conversation patterns that emerge and how the supervisors’ learning and supervisor competence developed.