This article examines the online discourse that took place in representative threads from two classes, seeking to document indicators that students did or did not engage in co-construction of knowledge. Stahl's (2006) social theory of computer supported collaborative learning (CSCL) is used along with discourse analysis methods to examine these course dialogues. Findings show the class that had a peer-like, consistent facilitative instructor and discussion anchored around questions and shared artifacts was more likely to engage in discussion leading to the negotiation of knowledge and understanding. This class relied on social acknowledgements, questions, and shared exploration of perspectives and theories throughout their discussion. These elements and strategies appear to be important components that make up for lower levels of tacit understanding in online environments, thus enabling learners to interact in social learning processes. The other class, which lacked a facilitative instructor, did not have the same results. Although interaction levels were equal and students carried topical motifs such as the phrase "faster, better, cheaper" from message to message, students in this other class did not engage deeply or develop new understanding of the course material through the discussion. (Contains 1 table and 2 figures.)