A preliminary investigation has been conducted into the prediction of field strength, of both wanted and interfering signals, at UHF. This report summarises the conclusions and purposes of further work. Terrain data for an area 25 miles (40 km) in diameter centred on Guildford were stored in the computer and used for the prediction of field strengths by various methods. The results were compared with detailed measurements of five transmissions in the Guildford area. The results demonstrated that existing methods of interference prediction require improvement, and that the prediction of wanted and interfering signals ought to be combined. A method of doing this, based on a stored bank of terrain data for the whole of the UK is now being developed.