In this paper, the Internet message board forum is proposed as an example of a community of practice (Eckert and McConnell-Ginet, 1992) in which contributors exhibit common linguistic conventions and forms of participation. The emergence of individual identities in interaction is examined in the genre-specific context of hip-hop Internet message boards. A corpus analysis of message board postings clearly shows that contributors systematically exploit the spoken and written qualities of the language of message boards, the " third medium" (Crystal, 2001) to identify themselves linguistically. Linguistic conventions or practices reveal a tendency among contributors to discursively construction their identities via a "social positioning of self and other" (Bucholtz and Hall, 2005) as experts or non-experts in the hip-hop community. Contributors' identities as experts or simply in-group members are further corraborated or established by the codification not only of non-standard pronunciations and grammar characteristic of speech, but also of non-standard orthography, which demands a written forum to be appreciated, as it is neutralized and unremarkable in speech. Because of the written and spoken qualities of message board discourse, both the content and the form of postings can be manipulated to showcase familiarity with hip-hop discursive practices. Internet message boards therefore represent the ideal forum for discursively constructing a hip-hop identity.