Exploring Mathematics Teacher Noticing of Whole-Class Discussions Across Career Stages Research on teacher noticing highlights differences between novice and expert teachers, yet little is known about early career and intermediate expertise levels and how these expertise-related differences emerge in central teaching tasks and content areas. Facilitating whole-class discussions represents a central teaching task, such as when fostering flexible strategy use. This study examines expertise-related differences in mathematics teachers’ noticing in observed video scenes of whole-class discussions on flexible strategy use in Grade 1 using Epistemic Network Analysis. The preliminary results show no substantial differences between intermediate and expert teachers but between beginning teachers and the other two expertise groups regarding their noticing focus and the cognitive structures underlying their noticing processes. 1 147-154 147-154