There have been a growing number of discourse studies in recent years on written academic genres produced by students. However, the master's thesis has not received as much attention as the PhD dissertation. This investigation of master's theses from three disciplines, biology, philosophy and linguistics, employs both discourse analysis and interviews with subject specialists. An analysis of the overall organization of the thesis with a focus on the structure of introductions reveals discourse features that distinguish this genre from research articles and also points to disciplinary variation within this genre. An analysis of the use of citations and the first person pronoun in the introductions shows that philosophy students create a much stronger authorial presence but establish weaker intertextual links to previous research than the biology students do in these texts. The linguistics students occupy a more central position in terms of these dimensions.