Purpose: The aim of this study is to analyze the interaction system between instructor and learners and strive for class improvement based on the evaluation. Methods: Flanders Interaction Analysis System classifies instructor and learner s speaking into ten items. Observer analyzed every verbal interaction in class and filled out classified table recording the number of adequate category every three seconds. Results: In this study, observed class spent 94.3% of time on teaching and learning activities. So it could be said that the class used time effectively without any waste. The instructor showed indirect teaching method and as a result, the students showed more initiative statements than simply answering questions. The major pattern was question → answering questions, and incidental pattern was lecture → initiative statement → silence or disorder → initiative statement → lecture. Conclusion: In medical education, small group lesson is one of the popular teaching methods where Flanders interaction can be analyzed effectively. Using such evaluation, we can promote better teaching and learning.