A study of distinctive characteristics of the style in which people communicate in computer-mediated communication (CMC), focusing on use of politeness conventions, is reported. Aspects of the concept of "face" and politeness in social interaction are first reviewed, and threats to speaker's and hearer's face are outlined. The relationship of politeness strategies, face-threatening acts (FTAs), and intentions is then examined. Previous research on politeness and discourse and on communication dynamics in electronic media are reviewed. The study itself is then detailed. Data were drawn from CMC on a bulletin board system (BBS) discussion, carried on over 10 weeks, on the topic of censorship on the BBS. Analysis of the communications was based on theory of politeness, with specific regard to FTAs. Results indicate that FTAs were a frequent feature of this topic, and that the social roles apparent to interlocutors in the outside environment were significantly altered in CMC. Discussion of the findings focuses largely on the role of the environment or the overall BBS community in the frequency of FTAs. It is also argued that examination of CMC can shed light on patterns in various communication factors, such as turn-taking and prosody. Contains 58 references. (MSE)