Since 1992 Arbitron has been developing and testing a personal portable meter (PPM) system capable of detecting exposure to any audio medium both in-home and out-of-home. With this system an inaudible identification code is embedded into the audio signal of radio television cable and other media outlets. These codes are then detected by pager- sized personal meters worn by respondents. The 1998 pilot in the United Kingdom was the first fully functional test of the entire PPM system. Fourteen radio and television stations encoded their signals and we recruited fifty respondents to wear the personal meters for the nine-week test period. Results showed that the encoding and decoding systems functioned as planned and respondent cooperation levels were high. All encoded stations were detected by the meters and respondents wore or carried the meters for a median fourteen hours per day. Given these positive findings we are proceeding with a larger scale PPM test panel in the United Kingdom starting in June 1999.