Critical thinking is a highly desirable goal of online higher education courses. This article presents qualitative data from a mixed-method study that explores how asynchronous discussions within online courses influence critical thinking among students. In this study, online discussions were related to higher levels of critical thinking, but qualitative data indicate that the way discussions are used and facilitated is vital for encouraging critical thinking. Online discussions typically have the purpose of creating a space and time for informal, open-ended thinking to occur. Critical thinking appears to be best encouraged among students when a more consistent emphasis is placed on the discussions, and when instructor facilitation is less frequent but more purposeful. (Contains 2 tables.)