The objective of this research is to study university composition entrance examinations as a discourse genre, in order to characterize its textual structure and to examine it as a social process in the pedagogic context. Theoretical aspects of systemic-functional linguistics (Halliday, 1994, Martin, 1989), genre studies (Marchuschi, 2002) and argumentation principles (Perelman, 1993, Breton, 1998) were applied to a corpus of 135 assignments. The texts, selected according to a range of grade variation, were written in Portuguese by applicants for courses of several areas from three universities located in different Brazilian states, two public institutions and a private one. As part of the analysis, textual configuration parameters were observed through the identification of the use of text types and argumentative structures found in the compositions. The analysis also aimed at the characterization of that particular genre in terms of academic discourse, leading it beyond its materialization in texts into the wider perspective of its relationship with the academic context. Research results show that applicants use different text types in their assignments, as well as several kinds of arguments, narratives being frequent as well as arguments with some emotional appeal. These characteristics, as well as the recurrent use of an oversimplified argumentative scheme and constant context explicitation (Biber, 1988, Oliveira, 2002) and with the constant use of nominalizations that refer to abstract ideas rather than processes, expressed through verbal forms that refer to actions (Halliday, 1994), point towards academic discourse. seem to contribute towards the characterization of these texts as not totally fitting academic discourse, thus frustrating examiners´ expectations and being evaluated by the committees as inadequate, due to lack of efficiency. On the other hand, the use of creative and humorous arguments, which are considered efficient, with reduced use of subjectivity marks also demonstrate that the texts analyzed are in accordance with the requirements of the academic context. Therefore, this research leads into the conclusion that university composition entrance examinations show both constitutive aspects inherent to academic discourse and also some dissonant characteristics typical of nonacademic texts. These results reinforce the need for the discursive characterization of this genre and its study as a social process in the Brazilian pedagogic context.