The purpose of this chapter is to present peer group mediation as one of the assessment practices within Teletandem Brasil, a Virtual Exchange (VE) project which uses tandem practice between university students of different countries for foreign language learning, carried out through videoconferencing tools. Peer group mediation sessions are regular meetings, in addition to the teletandem practice, and aim at promoting reflection on telecollaborative, intercultural, and language learning, and individual learning processes. Assessment is seen here as a practice by students, mediators, and peers that seeks to reflect upon and respond to information from dialogue, demonstration, and observation in ways that enhance ongoing learning. [For the complete volume, "Assessing Virtual Exchange in Foreign Language Courses at Tertiary Level," see ED624433.]