M205--STILE (“Students' and Teachers' Integrated Learning Environment”) project used a Computer Mediated Communication (CMC) environment to assist student learning on a Computer Science course which catered for both technical and non technical students. The participants, some 110 students and 9 tutors, were based in the U.K. and Europe. They were on-line for a period of 10 months, from February to November 1995. The provision of conferencing, email and WWW facilities enabled the students to: communicate with their tutors and fellow students; to download extra electronic course materials; and to post their computer code electronically, rather than by Royal Mail. This paper discusses the student-tutor, and the student-student exchanges in two of the tutorial conferences. It focuses upon the students' and tutors' perceptions of their interactions on-line. Students' and tutors' reactions suggest that the preparation of responses off-line provided time for students to reflect on their own understanding of the domain. Our results cast light on how improved understanding of the domain is possible through the different modes of communication made possible in a CMC environment.