Interaction in Korean Conversation. The Sociolinguistic Journal of Korea, 12(1). Among many topics in interactional linguistics, the research on reactive tokens has explored complex processes in which participants collaborate and develop each other's talk in a moment-by-moment fashion. The present study investigates properties of backchannels as tokens of social interaction in Korean conversation by adopting methodology of frequency analysis and conversation analysis. Through a frequency analysis of backchannels such as 'e', 'a', 'um', and 'ung', this research shows that backchannels most frequently occur at complex transition-relevance places where turn-constructional units and intonation units converge. Examination shows that major functions of backchannels in conversation can be summarized as in the three categories: (i) to signal passive recipiency of the on-going turn, showing attentiveness or acknowledging what is being talked about, (ii) to signal that the recipient is in agreement or of the same opinion with the current speaker, and (iii) to express recipient's affiliative or emotional attitudes such as sympathy toward the information provided, among others. Finally, this research shows that interaction-based study of backchannels in their interactional contexts can provide a better way of understanding communicative strategies and the relationship between conversation and grammar than do other traditional or formal approaches to grammar.