We analyzed students' patterns of participation, interaction and knowledge construction in asynchronous online case-based discussions in two Educational Psychology classes with different participation and interaction guidelines. We conducted quantitative analyses of the outlines of postings and transcripts of online messages from these group discussions to examine rates and patterns of participation and interaction. Qualitative analyses illuminated patterns of knowledge construction and helped us further analyze patterns of interactions. Based on our analyses, we found differences in rates of participation and patterns of interaction in the two sections, with higher, negatively skewed levels of participation and interaction in the more structured and guided discussions groups. In terms of content, we found that statements of clarification, elaboration, and grounded interpretation were related to the knowledge construction process most directly. Students' construction of knowledge appeared mainly selfreflective, even when it began by acknowledging the contributions of others, or clarifying information for others. The gradual posting of questions to help guide the discussions may be a more effective way than posting all the questions at once to help students construct the conceptual space, create relationships between conceptual knowledge and facts, and