ABSTRACT: CLIL (Content and Language Integrated Learning) is a term widely used in Europe to refer to different forms of content based education, often conducted in English. Earlier research on CLIL has tended to focus on matters of language learning or content mastery rather than on details of classroom interaction. This paper investigates how English is used in Finnish biology and physics CLIL classrooms. Classrooms are approached from a discourse-pragmatic perspective which involves close attention to social and interpersonal aspects of language use as it unfolds in authentic settings. The findings suggest that CLIL students claim ownership of English by the way they confidently use it as a resource for the construction of classroom activities. Students' code switching practices are another indication that they ascribe to an identity as users rather than as learners of English. Instead of using Finnish when their skills in English fail them, students use the L1 for affective functions; and the way in which they slip in and out of English and Finnish indicates that they view the classroom as a bilingual space. The findings thus point towards emerging bilingualism among the students.