Using a discourse analytic qualitative approach, we investigated the naturally-occurring discourse that arose as part of two kinds of regular course activities, synchronous and asynchronous computer-mediated discussions. The messages contributed by members of a graduate course were analyzed for the kind of discourse functions and the kind of politeness strategies they displayed. Results indicated that synchronous CMD afforded more information seeking, information providing, and social comments than asynchronous CMD. Asynchronous discussions were slightly more likely to allow for such functions as discussion generating, experience sharing, idea explanation, and self-evaluation functions than synchronous discussions. Proportionately the two modes were similar in how politeness was expressed. Finally, in relating politeness and function, we found more politeness indicators when students were posting messages with such functions as positive evaluation and group conversation management, functions that carried the potential for face threat, and the least politeness associated with messages serving the function of experience sharing. (Contains 6 tables and 1 figure.)