The hierarchical system of speech acts developed by Sinclair and Coulthard (Towards an analysis of discourse: The English used by teachers and pupils. Oxford: Oxford University Press, 1975) to describe interaction in traditional classrooms and later applied to face-to-face communication by Stenstrom (An introduction to spoken interaction Series: Learning about language. New York: Longman Publishing, 1994) and asynchronous conversations by Harrison (E-mail discussions as conversation: Moves and acts in a sample from a listserv discussion. Linguistik online, 1, 1998) is used here to analyse interaction in an online graduate education context that employed a peer group discussion model. Message content was analysed to determine if there exists an online variant of teacher talk and learner talk and the extent to which participants adapted previously identified speech components and patterns. Quantitative and qualitative differences in the organisational, interactive, and content-related features of both teacher's and learners' contributions were found. Participants in asynchronous text-based interaction used a rich variety of speech acts, some of which are used in traditional classroom interaction and peer group conversations that are conducted in both face-to-face and asynchronous contexts, and others that are unique to the online educational environment.