The introduction of practice theory into sociolinguistics is an important recent development in the field. The community of practice provides a useful alternative to the speech-community model, which has limitations for language and gender researchers in particular. As an ethnographic, activity-based approach, the community of practice is of special value to researchers in language and gender because of its compatibility with current theories of identity. An extension of the community of practice allows identities to be explained as the result of positive and negative identity practices rather than as fixed social categories, as in the speech-community model. The framework is used here to analyze the linguistic practices associated with an unexamined social identity, the nerd, and to illustrate how members of a local community of female nerds at a US high school negotiate gender and other aspects of their identities through practice. My thanks to Janet Holmes, Chris Holcomb, Stephanie Stanbro, and members of the Ethnography/Theory Group at Texas A&M University for comments on and discussion of the ideas in this article.