This paper considers different uses of asynchronous discussion in distance education, highlighting the benefits to learners and the issues that need to be considered. The context is the use of computer conferencing by distance learners of technology at the UK Open University. The paper focuses on two courses where computer conferencing has been used in different ways: for optional peer support; and for assessed group activities. A number of questions about the use of asynchronous discussion are considered in the light of experience from these two contexts. What are students' reasons for participating, or not participating? Can students learn from each other without tutor intervention? Can group work be carried out effectively by student teams whose members never meet?