Online discussion plays a unique role in face-to-face and distance teaching and learning. Interaction and student cognitive engagement during the online discussion are critical for constructing new understanding and knowledge. This article analyzes types of interaction that occur during online discussions, examines levels of student cognitive engagement in each discussion, and explores their effects on and implications for learning and teaching in higher education. By combining methods of social network analysis with qualitative content analysis, the article explores new methodologies for analyzing participation, interaction, and learning that take place online, and suggests areas for research in learning and teaching online.