The purpose of the present study was to examine the nature of the discourse generated by two different online approaches to mathematics teacher professional development. Thirty mathematics teachers participated in online activities involving analysis and discourse about artifacts of teaching practice. Half were randomly assigned to a group that analyzed and discussed students work samples, and the other half to a group focused upon descriptions of classroom teaching episodes. Teachers formed threads of conversation on asynchronous discussion boards as they considered the different aspects of each artifact. Within the threads, different orientations toward the reform agenda in mathematics education were shown. Some messages were strongly rooted in the reform paradigm, others in the traditional paradigm, and many others contained elements characteristic of each paradigm. The distribution and characteristics of the messages reflected teachers' frequent attempts to try to reconcile the largely incompatible paradigms undergirding reform-oriented and traditional approaches to mathematics instruction. This paper describes the nature of the discourses occurring within each group of teachers with the aim of providing empirical grounds to inform the actions of teacher educators and researchers designing online learning environments that attempt to bring teachers more fully into the reform-oriented discourse about teaching mathematics. (Contains 2 tables.)