This report summarizes a five-volume research report on the classroom use and impact of ThinkAbout, an instructional television series designed to strengthen the reasoning skills of fifth and sixth graders and to review and reinforce language arts, mathematics, and study skills. It describes results of a 1979-80 research study which used three complementary methods of determining classroom use and impact: student testing in 241 classrooms in Iowa, Mississippi, Oregon, and Pennsylvania; four questionnaire surveys of teachers, of which over 2,000 were returned; and case studies. The results reported indicate that (1) the most striking program impact was on the curriculum in the user classrooms, in that topics were addressed that ordinarily were not covered in the fifth and sixth grades; (2) the series was used in varied ways with varied results; (3) the school and classroom context of instructional television affects its introduction and use; (4) internal organizers and outside support materials were necessary for reinforcement; and (5) additional teacher inservice work is needed. Summaries of three case studies, drawn from the second volume of the report, are included. (Author/LMM)