Which communication mode(s) do experienced distance learners choose as they collaborate on tasks, and what do they talk about in each mode? How do the participants choose modes for various aspects of a task, and which phases of knowledge construction are present? In this study, case study and computer-mediated discourse analysis procedures are used to investigate transcripts and individual reflections of 10 small groups of distance learners. The findings reveal that the discussion forum was used significantly more often for conceptual moves and for later phases of the knowledge construction process. Email was used more for social moves, and chat was used more for later phases of knowledge construction. Implications for providing groups with various CMC modes to complete tasks and for advising novice online learners about the affordances of each mode are addressed.