The purpose of this research is to investigate the discourse of English as foreign language coursebooks and its relation to students´ construction of social identities. In order to observe socio-discursively how these books represent the world and the cultural contexts related to the English language; to investigate the extent to which they offer voice opportunities to students; and to identify the beliefs they reflect concerning the teaching and learning of English, this thesis adopts a systemic-functional approach to language, a socio- interactionist view of teaching and learning and a critical perspective of discourse and culture. Adopting a non-essentialist view of social identities and considering the insertion of society in post modernity, this research analyzes twelve English coursebooks, from six different series, at beginner and intermediate levels. Books were selected according to variation parameters involving communicative objectives, target audience, both place and date of publication, and consumer market. Topics and cultural contexts were investigated to identify the world view expressed in each book (ideational metafunction); exercises and activities were both related to the social roles imagined for projected book users and to students´ voice opportunities (interpersonal metafunction); finally, the structural organization of the materials (textual metafunction) was studied to identify authors´ beliefs concerning the teaching and learning of English as a foreign language. The analysis showed that the choice of topics and cultural contexts provides a world view that may lead students to adopt certain identities which are presented as the right ones, socially acceptable and legitimated in several books. Results also indicate, in eight out of the twelve books analyzed, the representation of an American and European world view, where status and visibility are crucial to success, in accordance with post modern society. The organization of the materials, which generally thematize grammar, shows that most authors understand the teaching and learning process as a set of formal rules to be apprehended and reproduced, rather than a way of acting in the world. The analysis of the exercises and activities showed that there is little space for learners´ cultures and few opportunities for them to show their voice and perform their identities freely. Results of this research point to the importance of discussing these issues and making students, teachers and researchers who deal with coursebooks aware of the social and discursive force inherent to the materials, which can interfere with the construction of identities, worlds and beliefs.