This paper presents a methodology designed to explore the role of context in collaborative knowledge construction activity in asynchronous web-based discussion. The discussions of two student groups participating in a web-based teacher education course were compared. The comparison aimed to highlight the differences and similarities between the groups' knowledge construction activity through studying the thematic structure, communicative functions and contextual resources used in their discussions. The results indicated that the different backgrounds of the two student groups influenced the way context was created and interpreted, and how meanings were negotiated. The differences and similarities between the groups' activity illuminated the situated and mediated nature of learning. The possibilities of the methodology used in this study for evaluating collaborative knowledge construction in context are also discussed.