Instructional supervision is the use of monitored service for preservice training. It is supervision of more experienced students in order to teach less experienced ones. As a pedagogy of counselor education, instructional supervision is supervisory because it monitors an actual client, and instructional because it uses supervision as a pedagogic tool. In this study, prepracticum counseling laboratory students observed and participated in the live supervision of a practicum counselor. The counselor showed videotaped client sessions to a supervisor who was also the lab students' teacher. Students followed the practicum case over the semester, meeting weekly with the counselor and supervisor to observe and participate in supervision. The model of instructional supervision proposed is a deployment of direct and vicarious learning opportunities defined as multiple roles and activities that vary for the same individuals. Roles are not assigned but emerge naturally as a result of overlapping tasks, interrelated perspectives, and group participation. The research of Goodyear and Bernard (1998) is used to examine the distinction between supervision and training. A brief review of instructional supervision literature within counseling supervision is presented. Finally, the model and theory of instructional supervision is described. The model is composed of four principal parts: target, purpose, format, and roles. Supported by the four principles, the model has the following attributes: vicarious and immediate observation; approximation; reflexibility and feedback; and alternative constructivism. The model may be described in terms of development and individual differences, cognition, affect, and professional acculturation. (Contains 80 references.) (MKA)