This article describes an approach based on structuration theory (Giddens, 1979, 1984; Orlikowski, 1992, 2000) and communities of practice (Wenger, 1998) that can be used to guide investigation into the dynamics of online question and answer (Q&A) communities. This approach is useful because most research on Q&A sites has focused attention on information retrieval, information-seeking behavior, and information intermediation and has assumed uncritically that the online Q&A community plays an important role in these domains of study. Assuming instead that research on online communities should take into account social, technical, and contextual factors (Kling, Rosenbaum, & Sawyer, 2005), the utility of this approach is demonstrated with an analysis of three online Q&A communities seen as communities of practice. This article makes a theoretical contribution to the study of online Q&A communities and, more generally, to the domain of social reference.