In a study of the use of videotaping to modify teacher behaviors, five teachers in a reading and learning skills center were filmed in interaction with students; they then observed and measured their own "on-task" and "off-task" behaviors while viewing a series of taped sessions. A control group of two teachers had pretest and posttest filming only. This paper explains the study procedures and provides examples of three measures used: a questionnaire that measured teachers' attitudes toward the videotaping before and after the study; "on-task" and "off-task" checklists that measured the teachers' knowledge of appropriate and inappropriate behaviors; and tally sheets on which teachers recorded their observed behaviors at ten-second intervals. The paper then presents the study results, which revealed that both the control and experimental groups increased their percentages of on-task behavior from pretest to posttest filmings and that teachers in the experimental group found the use of videotaping very helpful in improving teaching behaviors. Tables of collected data are included. (GW)