The present paper examines the realisation of disagreement on two discussion boards on a Taiwan-based BBS (Electronic Bulletin Board Service) to identify the linguistic devices utilized in online disagreements and to analyze the concept of face on BBS. Disagreement has long been recognized as an intrinsically face-threatening act (Brown & Levinson 1987) and needs extra management during its realisation to maintain the relationship between the addresser and the addressee. In this paper, members of BBS boards are found to draw on various kinds of resources, such as their oral language repertoire or from the medium of technology in projecting disagreement (Baym 1996; Golato & Taleghani-Nikazm 2006). Various posts and boards show different tendencies in their strategic use and these tendencies are in line with their identity, interactional purpose and behavioural norms. It is then argued that these strategies are enacted to negotiate identity and relationships— or face, the combination of these two notions— in the online community of practice. In other words, these different behavioural patterns reveal the variety in online communities. The findings in this paper suggests that Watts’ (2003) and Spencer-Oatey’s (2005, 2007) notions of face are more useful theories for interpreting relational management in an online context. Watts stresses that face is constituted in interaction(s), while Spencer-Oatey emphasizes the relationship between face and identity. In this light, one is able to understand the complex and ever-changing human interaction better by recognising different factors, especially in the non-traditional computer medium. Drawing on the observations of this paper, a multidimensional and interactive concept of face in online communities is proposed in light of these two theories.