A discussion of the economic and technical advantages of satellite-based instructional radio systems of 50 to 200 channels compared with educational TV and its necessarily more limited number of channels. The argument for radio rather than TV centers around four propositions: (1) The evidence shows no significant difference between the instructional effectiveness of TV and that of radio. (2) An ETV channel would use around 200 times as much of the available radio spectrum as a radio channel. (3) The dollar cost of radio per channel is no more than a tenth or twentieth that of TV. (4) To the extent that the preparation of instructional material may be an important limiting factor, the simplicity and lower cost of radio programming are an argument in its favor. 12 pp. Refs.