A guide for group discussion leaders that may be useful for medical school teachers is presented. One objective is to help the teacher know when group discussion is appropriate. It is suggested that both the lecture method and group discussion can facilitate cognitive learning but at different levels, and that group discussions are helpful if there are prior attitudes that interfere with cognitive objectives. The following approaches to group discussion are recommended: the learners should share leadership in the discussion process; the teacher should demonstrate an attitude of self-awareness, openness, and tolerance of learners' opinions; and the teacher should maintain a relaxed attitude. A taxonomy including six characteristics is presented, which classifies the discussion as either teacher-centered, group-centered, or learner-centered. Guidelines cover planning the group discussion, including the physical facilities and group size, as well as the following teaching techniques: questioning, brainstorming, and case-based reasoning. Finally, the evaluation of group discussion is covered. An observation tool is appended that includes the following: organization of the subject, teacher traits, session characteristics, session planning, teaching techniques, and session evaluation. (SW)