This paper describes an extension of Stahl’s (2000) model of collaborative knowledge building. Three cycles of reflective thinking activities are added to the original model in order to support the investigation of the role of reflection in collaborative knowledge building. The model is combined with activity theory to make reflective thinking activities the unit of analysis. This fosters the investigation of participants articulating and making explicit their own knowledge (cycle 1), the analysis of participants engaging in collaborative reflective discourse to develop shared understanding (cycle 2), and studying the participant’s use of reflective conceptual artefacts (cycle 3) to formalize and objectify knowledge. The extended model also supports the study of how collaborative technology may support reflective activities. The paper concludes with comments on how this model may be applied
