Interaction plays an important role to the success of distance learning. As most distance learning environments utilize mainly asynchronous Computer-Mediated Communication (CMC) systems, interaction research that focuses on synchronous CMC is largely ignored. This study scrutinize the patterns of learner-learner interaction in a distance-learning environment. Student interactions in synchronous and asynchronous CMC systems were both compared. Results of the research suggest that constructivist-based instructional activities, such as student- moderated discussion and small group cooperative learning, are conducive to interaction. Overall, a higher percentage of social-emotional interactions occurred in synchronous mode than occur in asynchronous mode. Students spent more time in task-oriented interaction in asynchronous discussions than in synchronous mode. In moderating online seminars, student moderators that followed the guideline of Student-Centered Discussions (SCD) could encourage full participation of online seminar. Recommendations on the design of instructional activities and interactive interfaces were also made for the improvement of distance-learning environments.