This paper outlines some findings of a three-month investigation into the effects of students' interpersonal relationships on communication in two EFL classrooms in a Japanese university. Data was collected to identify and describe the various social subgroups that existed within the classes, and samples of classroom discourse were then analysed to investigate how students' social positioning in the classroom affected the observed interaction. The analysis suggests that the relationships that students develop in the classroom do have implications for interaction, and that conducting research into those relationships could have a positive impact on teachers management of classroom interaction. (Contains 4 figures.)