This article explores the use of blogs for pre-service language teacher education in two national settings, the UK (University of Cambridge) and the US (University of South Florida). Taking two approaches to blogging and to learning through blogging (one based on self-reflection and a constructivist approach and one based on social and collaborative learning and a sociocultural approach), the research examines how pre-service language teachers both use and understand the affordances of blogs for their professional development. Data were collected from the participants' blog entries during their eight/nine month courses and from individual interviews conducted and analysed inductively. Some distinct themes emerged from the two settings. In the UK setting, there was deep analytical reflection on professional development, on professional identity and on change, with the participants perceiving the benefits of the blog to be the distance it provides from events and the cathartic effects of writing. In the US setting, findings suggest that the blog was used as a space for joint sharing of resources and ideas, and for co-constructive learning. Participants noted the affordances to be sharing information, developing professionalism and collaborative learning. While the approach to blogging was different in the two settings, the engagement in both was dialogic; the blogs functioned as a "thinking device" that enhanced professional development. Their use may transfer from pre-service teachers' learning to their teaching. (Contains 1 table and 4 figures.)