Plagiarism is regarded as a heinous crime within the academic community, but numerous accounts in the literature on first- and second-language writing suggest that some writers plagiarize without intending to transgress academic conventions. However, because the evidence for this form of source use is almost exclusively anecdotal, many questions remain, chief among: how widespread is insufficiently attributed source use? Can evidence be found for the claims that such writing is unintentional? And can lack of intention be accepted as an explanation for plagiarism in the work of students who have been informed about how the English-speaking academic community views the act? This paper will report a study of the writing of seventeen postgraduate students in four academic areas: science, engineering, social science and humanities. Source reports in the student-generated texts were compared to the original sources in order to describe the relationship between the two. Interviews were also conducted with the student writers and their supervisors. The student writing was found to contain textual features which could be described as plagiarism, but the writers' accounts of their work and the textual analysis strongly suggest absence of intention to plagiarize, thus providing empirical verification of similar suggestions in the literature.