This licentiate thesis investigates teachers’ and students’ cognitions of bilingual subject-specific literacies. The thesis builds on three different studies, referred to as case studies, conducted in Content and Language Integrated Learning (CLIL) study programmes in the Swedish upper secondary school. Participants’ views and experiences of two languages of schooling, English and Swedish, were elicited in interviews, and analysed thematically. To gain understanding of the three studies in combination, a further analytical framework was developed and tested. In this analysis, participants’ descriptions, explanations and reflections on teaching and learning curriculum content bilingually emerged as three-dimensional discourses. In the first study, new and experienced teachers’ challenges and strategies were in focus. The biology and civics teachers, who were new teachers, and new to CLIL, found teaching through the second language of schooling, English, time-consuming and demanding. They expressed concern about limited communication and learning in the classroom. The mathematics teachers, who had long teaching experience, and of teaching in the CLIL programme, had developed strategies to meet perceived challenges, for example, they had designed parts of lessons in a monolingual mode, and parts of lessons in a bilingual mode. The second study explored intermediate CLIL teachers’ rationales for language choice in teaching. The biology and history teachers found that access to English, as afforded through the CLIL framework, coincided well with the new syllabi for their school subjects. For instance, the history teachers could use web-based study materials in English in class, and found teaching and learning more authentic than in the mainstream, Swedish-speaking, study programmes. The biology teachers mentioned that access to English terminology facilitated the teaching and learning of complex subject-specific content areas. It functioned as a potential source to enhance students’ understanding. The third study documented students ́cognitionsof CLIL. The views of upper secondary students studying curriculum content through English were overall positive. However, results showed that their experiences of CLIL varied with school subject. Whereas studying mathematics through English was reported to be conducive to learning and understanding, learning civics through English only, or trying to listen to lectures in civics, where teachers would change languages seemingly without a rationale, were perceived as less conducive to learning. / <p>At the time of the licentiate defense, the following paper was unpublished and had a status as follows: Paper 2: In press.</p> / Content and Language Integration in Swedish Schools (CLISS)