Today, a variety of web-based learning environments have been developed for educational purposes, especially in higher education and continuing education courses. At the same time many studies have reported how networked interaction in many learning projects results in superficial and experience-based discussion, and does not reach the level of theory-based reflections and argumentation [e.g. W.F. Admiraal, D. Lockhorst, T. Wubbels, F.A.J. Korthagen & W. Veen (1998) "Computer-mediated communication in teacher education: computer conferencing and the supervision of student teachers," "Journal of Learning Environment Research," 1(1), pp. 59-74]. Challenged by this, this research project investigates social construction of knowledge in Computer-Supported Collaborative Learning settings, especially the possibilities and problems of shared virtual environments in supporting learning and interaction. The first of two related sub-projects is focused on using shared workspaces and cognitive tools to support co-construction of understanding in complex science and civic phenomena in secondary school settings. The other project aims to develop the kind of pedagogical models for teacher training purposes that would facilitate deeper-level interaction and argumentation in networked communication.