Background. Electronic discussion lists are used by many groups, including GPs, for communication and information sharing. The technology offers potential for formal learning and professional development. Various models have been proposed to describe the dynamics of such 'virtual' forums, and research is required to explore how such a discussion list might support professional development. Objective. We aimed to explore the use of the Internet-based discussion group gp-uk by GPs and their colleagues. Methods. We carried out a qualitative study of the electronic text generated by GPs and colleagues on an academic medical discussion group. Results. The list gp-uk has features of a collaborative medium, in which the audience are also contributors. There is support for a 'critical mass' model, in which a relatively small number of members contribute on a regular basis. There is little support for a 'discretionary database' model of more formal sharing of specific factual information. Conclusions. The findings indicate a model for a 'virtual classroom' for computer-mediated learning and professional development. A critical mass of participants is a requisite, the list should be facilitated to guide discussions and supporting resources such as an Internet web-site should be provided.