This paper discusses stylistic conventions within broad disciplinary groupings in the language of doctoral theses. It argues that the language conventions in doctoral thesis texts reflect spohisticated learning of key disciplinary norms governing the conception, production and reporting of knowledge in particular fields. The paper shows that many conventions are subtle; they may not be readily identifiable to experienced scholars, yet doctoral students are expected to learn and master them, suggesting that discipline-specific writing norms and conventions are learned largely by tacit means during doctoral study. The paper reviews the nature of linguistic forms in doctoral theses and identifies the underlying epistemological and cultural influences which shape the writing. Doctoral theses from a range of disciplines are examined closely. Attention particularly is directed to the overall structure of argument and the techniques for coherence; the conventions for citing, acknowledging and making judgements about previous research; and the nature of the technical language of the field.