Objectives : This study was conducted to evaluate the effects of the personal stereo system on the hearing in adolescents. Methods : A total of 68 adolescents(age: 13-18 years) who visited the ENT Department at a University Hospital in Daegu were personally interviewed. The questionnaires were about general characteristics of the subjects, the time of personal stereo system use (year, hour) and place. Cumulative exposure to the personal stereo system was calculated by the product of the total years and the daily hours of their use. Pure tone audiometry was performed and the hearing threshold was measured at 500, 1000, 2000, 4000 and 8000 Hz. Results : The average time of using a personal stereo system a day was about 3 hours and 75% of the subjects used a personal stereo system for 2-5 years. The elevation of threshold was more prominent in the subjects who used personal stereo systems for 4 years and more compared with those subjects who used them for 3 years and under. The elevation of hearing threshold was also more prominent in the subjects who used personal stereo systems for 4 hours and more a day compared with those subjects who used personal stereo systems for 3 hours and under a day. The elevation of hearing threshold was more prominent in the subjects who used personal stereo systems for 13 hour. years and more compared to the subjects who used them 12 hour. years and under. Conclusions : These results suggest that the elevation of hearing threshold can happen to adolescents who used personal stereo systems for a long time. In order to prevent hearing loss, we need to teach adolescents appropriate usage of the personal stereo system and hearing tests should be included in the periodic school-based physical examination for the adolescents.