Twenty years ago, anyone proposing to help teachers with the problem of classroom discipline had few resources at hand. It was approximately at that time that Jacob Kounin began a series of investigations that have changed our way of talking and thinking about classroom discipline. He changed our focus from a sterile concern with exercising discipline to a productive concern with smooth classroom functioning. In doing so, Kounin identified a set of data-based concepts about classroom management and, through his investigations, became convinced of the usefulness of studying the classroom as an ecological entity rather than as an assemblage of individuals alone. Kounin identified four dimensions as correlating with a teacher's management success: (1) with-it-ness; (2) smoothness (of presentation); (3) momentum; and (4) group focus. These management techniques are always related to the setting and change accordingly. Also noted as being important was the continuity, insulation, and protectiveness on the teacher's part of the signal system. Kounin was also one of the first to make systematic use of videotape recording as a data source for the analysis of classroom behavior. (JMK)