This article describes the experiences of an inservice professional development project for secondary mathematics teachers as project staff struggled to build professional community through online discussions of teaching mathematics with technology. Data from two consecutive years of the project are reported and analyzed in terms of Riel and Levin's (1990) framework for network participant structures. The data that we report show that while structural adjustments were made by project staff in an attempt to increase online participation from one year to the next, the discussion forum received little significant use. This failure occurred during two years of workshops that were well-attended and judged highly effective by the participants. Based on our analysis of this data we discuss difficulties associated with the use of online discussion forums in the context of teacher professional development and we make recommendations for teacher educators who wish to incorporate online discussions in their work.