The purposes of this study are (1) to estimate the number of commercial UHF television stations that are likely to come on the air between the present and 1990, and (2) to determine whether spectrum resources already allocated will be adequate in meeting this demand. Collaterally, the study seeks to determine whether some spectrum space now allocated to commercial UHF broadcasting will continue to lie idle and may be subject to reallocation to competing services. Taking 1974 as a base year, the study examines relationships among the existing stations and such variables as the number of television households, the growth of cable television, and the competition from overlapping television markets. It projects the number of stations along various paths into the future depending upon certain assumptions, including new services such as pay television. It concludes that the number of UHF commercial broadcasting stations will continue to rise between now and 1990. However, except for a few scattered markets, existing spectrum assignments appear adequate to accommodate this growth. The report is supplemented by a series of appendices, one of which is a model of the determination of the number of viable UHF television stattions. (WBC)