Educational authorities in many developed countries are funding the development of online environments that aim to facilitate teacher professional learning through collegial, reflective sharing of practice. But is this a case of "if we build it they will come"? Are teachers ready to share ideas and experiences in online communities of practice to enhance their professional learning? This article examines the experiences of teachers and school leaders who participated in a pilot online environment created to support teacher professional learning and it identifies factors that facilitated use of the online environment and factors that acted as a deterrent to use. The article identifies three key sets of conditions that deter teachers' use of online communities as a model for professional learning. These include a lack of perceived commonality of purpose; an underdeveloped culture of shared, critical reflection about practice; and lack of familiarity and experience amongst teachers in using computer-mediated communications tools as part of their regular practice.