Although much of the research into source use by international students has tended to focus on issues of plagiarism, there has recently been recognition that their difficulties in this respect may be more pedagogical than moral. However, much remains to be known about the nature of such students? source use. In order to throw light on the ways in which novice L2 writers use source material in their writing and to understand what difficulties they experience, this paper reports on a small case study involving a group of Japanese postgraduate students. Analysis of five Pre-Master?s dissertations written by these students, as well as interviews conducted with the writers, revealed that they varied in their ability to handle source material effectively. In many cases, their use of source material appeared to be symptomatic of weak authorial stance and apparent lack of a clear argument. Based on these findings, the study concludes with the recommendation that instruction on the use of source material focus to a greater extent on its rhetorical function in constructing knowledge.