Introduction A knowledge of interference protection ratios (the ratio of wanted-to-unwanted signal power at the receiver input) as a function of subjectively assessed picture quality is vital to the planning of television systems. Thus protection ratios for interference between two amplitude-modulation@ vestigial-sideband (AM-YSB) signals have long been necessary in planning terrestrial broadcasting systems. Now@ the many allocations of the frequency bands to the BSS on a shared basis with various terrestrial and space services have made the subject of protection ratios required by many different modulation methods of great importance. Indeed with the imminence of digital transmissions both as interferers and as wanted signals a knowledge of protection ratios among such signals and between them and analogue signals is also necessary. This Report summarizes the results of protection ratio tests made by several administrations in cases where the wanted and unwanted signals are modulated by colour television signals or other transmissions such as multiple sound channels. (See Note.) In considering these results@ it should be noted that particular combinations of signals are not@ in general@ confined to a single band of frequencies. Thus the protection ratio measured for interference between frequency-modulation and amplitude-modulation@ vestigial-sideband signals is important not only for sharing in the band 620 to 790 MHz but also for the bands 2500 to 2690 MHz and 11.7 to 12.5 GHz. Note. - Protection ratio data for interference between an amplitude-modulation@ vestigial-sideband or a frequency-modulation