The aims of this study are: (1) to examine to what extent critical care and advanced practice nurses? participation in an online listserv constituted a community of practice, and (2) to explore how the nurses use electronic media to communicate with one another. Findings suggest that the online listserv environment, as a whole, did function as an online community of practice, where participation not only served as an avenue for knowledge sharing situated in the actual context of the nurses? everyday work experience, but also helped to reinforce identity of the nursing practice itself. Motivations to participate included a way to network with others who shared a similar working situation, and an opportunity to learn new knowledge and work practices. The most common type of messages posted was "Sharing knowledge", followed by "Solicitation". Regarding the types of knowledge shared, the most common ones were "Institutional Practice" and "Personal Opinion".