Non native speakers of English wishing to study at tertiary level in English speaking countries are increasingly required to prove their English language competence by taking an internationally recognised test such as the Test of English as a Foreign Language (TOEFL) and the International English Language Testing Systems (IELTS). This article reports on the analysis of a corpus of scripts written in response to a section of the IELTS test requiring students to write a short argument essay. The analysis focuses on the range of argument structures deployed by students, aiming to establish the extent to which particular strategies are associated with the band score awarded for the task. The article also considers possible effects of the design of the test on student responses. (Contains 1 table and 3 figures.)