This study examines online messages in a discussion forum that a group of K-12 history teachers used to discuss curriculum implementations as part of their professional development. It has 3 main research foci. First, it focuses on identifying the types of assistances provided to the teachers in an online forum. Second, it examines teachers' cognitive thinking levels exemplified in their online messages. Third, it investigates the relationship between the assistance provided to teachers and the thinking levels they exemplified online. In addition, the study presents data from interviews with forum users to help validate findings attained through examining the online messages. Findings show that various assistance types and forum users' perceptions of online communication may have influenced teachers' levels of thinking during online discussions. (Contains 2 tables and 6 figures.)