A SERIES OF EXPERIMENTS WAS CONDUCTED TO TEST THE EFFECTIVENESS OF TELEVISED INSTRUCTION. THIS REPORT, THE FIRST IN A SERIES, STUDIES THE APPLICATION OF PRETESTING PROCEDURES TO BROADCAST TELEVISION. EXPERIMENTAL COMPARISONS WERE MADE OF THE EFFECTIVENESS OF A PREVIEW VERSION OF A TELEVISED LESSON AND ITS REVISED COUNTERPART. THE EXPERIMENT WAS REPLICATED USING DIFFERENT LESSON CONTENT ON HEAT, ONE ON CHEMISTRY, DIFFERENT INSTRUCTORS, AND DIFFERENT CLASSES OF STUDENTS. EACH LESSON WAS A PREVIEW SHOWING FOLLOWED BY AN ACHIEVEMENT TEST. ANALYSES OF TEST ITEMS REVEALED WHAT WAS NOT BEING TAUGHT EFFECTIVELY. LESSONS WERE REVISED ACCORDINGLY. LATER, PREVIEW AND REVISED VERSIONS OF THE LESSON WERE TELECAST SIMULANEOUSLY. STUDENTS WERE THEN TESTED. RESULTS SHOWED AN AVERAGE IMPROVEMENT VARYING FROM 6 TO 26 PERCENT FOR STUDENTS WHO WATCHED THE REVISED VERSION OVER STUDENTS WHO WATCHED THE ORIGINAL, PREVIEW VERSION. TEST RESULTS FOLLOWING A LESSON PREVIEW WERE CONSIDERED AN EFFECTIVE SUBSTITUTE FOR STUDENT-TEACHER INTERACTION. TELEVISION ENABLED THE INSTRUCTOR TO TAILOR HIS PRESENTATION TO THE NEEDS AND ABILITIES OF HIS PARTICULAR STUDENT AUDIENCE. RELATED REPORTS ARE ED 003 646 THROUGH ED 003 653. (HB)