This study investigates the extent to which mentor teachers experience reflective moments during mentoring dialogues. Any description of the phases of professional growth includes the degree to which explicit action goes hand in hand with deliberate consideration and thinking. There is little known about the thought processes of mentor teachers during their dialogues with students in the workplace. This study analyses 60 dialogues of experienced mentor teachers, both before and after they receive training in supervisory skills. Two methods of investigation are used: firstly, a stimulated recall interview following the dialogue, which traces reflective moments and secondly, a specially developed push-button device used to record these moments as they occur. During mentoring dialogues, the mentor teachers' behaviour comprises few reflective moments. Significantly, these occur more frequently after training. This seems to not only confirm the view that much of professional behaviour occurs automatically and instinctively, but also to support the premise that cognitive processes are important in the acquisition of supervisory skills. The combination of both methods of recording seems to make it possible to achieve a more accurate registration of the number of times these moments occur.