While the intonation unit (IU) has been characterized as a cognitive unit in earlier research, recent studies have revealed its interactional aspects as well. Using data from spoken Korean, this study presents evidence which shows that the IU is motivated both cognitively and interactionally, and proposes an interpretation of the IU that incorporates both of these bases, arguing that the IU serves as an interactional resource that speakers and listeners may rely on in organizing their talk, while it is the cognitive nature of the IU itself that allows the IU to serve as such a resource.