This study had its origins in a concern that teacher librarians in Australia were disadvantaged in the development of their professional learning due to their professional and often geographical isolation. Specifically, the study sought to determine whether usage of an online discussion group (listserv), OZTL_NET, was associated with the enhancement of teacher librarians' professional learning. The study concluded that online learning communities may provide appropriate contexts for teacher professional learning and that, in relation to the case of OZTL_NET, various aspects of the concept of online learning communities and, to a lesser extent, communities of practice, were portrayed in the listerv.