Generally the promotion of multilingualism is desired and sought. However, research showed that migration-induced multilingualism is often considered as an obstacle for learning. This is evident in monolingual oriented teaching strategies, models of schools, curricula. A 'monolingual habitus' (Gogolin 1994) is the context-setting for school practices. On the other hand, research on language acquisition provides evidence of the positive potential for learning, brought about by multilingualism (e.g. higher meta-linguistic skills or the acquisition of additional languages, Riehl 2006). Consequently, the recognition and use of multilingualism in the mainstreamed classroom and as a resource for learning should be promoted. Much research has been conducted on the attitudes of teachers towards an active use of multilingualism in class, whereas little has been done on how pupils use their multilingual resources for learning, particularly within content-matter classes of more advanced school levels. The paper will present data analysis and excerpts from a video study conducted in Hamburg, where the central research question focussed on the role of multilingualism for learning in subject-matter classes. In the study 59 classroom hours were recorded with three cameras and an MP3 recorder was placed on each pupils, so that all interactions could be fully captured and analysed.