This paper is based on a multiple-case study of the learning process in three asynchronous computer conferences. The conferences were part of the distance learning component in doctoral degree courses in computing technology in education offered at an American university. The conferences were analyzed from a number of perspectives, the emphasis in this paper being on the dimensions of interaction and cognition. Although similar interaction patterns were identified in the three conferences, each conference also showed distinctive patterns, which were related to factors such as instructor moderation, structuring of the instructional task and the emergence of student moderation of the discussion in specific threads. Three models were used to evaluate cognition: Bloom's Taxonomy (Bloom, Engelhart, Furst, Hill, & Krathwohl, "Handbook 1, Cognitive Domain," Longman, London, 1956), the SOLO Taxonomy (Biggs & Collis, "Evaluating the Quality of Learning: The SOLO Taxonomy," Academic Press, New York, 1982) and the "Practical Inquiry Model of Cognitive Presence" (Garrison, Anderson & Archer, "The American Journal of Distance Education" 15(1)7, 2001). Correspondences were found among the three models and all three conferences were characterized by higher-order thinking. When higher-order thinking was defined in terms of the distributed cognition occurring during practical inquiry, the advanced phases of cognition were found to be related to synergistic interaction in the conference threads. The findings serve to define the knowledge-building processes occurring in asynchronous computer conferencing. They also lend support to views of learning as dialogical and to social constructivist approaches to learning and teaching.