This article investigates the speech of Humanities and Natural Science instructors and students in 32 German and 32 American lectures and interactional classes. It examines how English and German structural markers and question tags contribute to variations of style in response to social and contextual factors in academic discourse. The data analysis couples qualitative, discourse-analytic methods with a quantitative sociolinguistic analysis. Among instructors and students in both cultures the factors of conversational role, academic discipline, and conversational mode – not gender – are most influential in the use of structures investigated. It is argued that these results arise from discourse restrictions in academic speech, such as turn type pre-allocation, speech length restrictions, as well as varying knowledge building and teaching strategies. A cross-cultural comparison shows remarkable similarities when it comes to a link of several structures to conversational role and discipline. Differences are primarily frequency of use of some of the structures investigated.