OBJECTIVE. The goal was to assess risky and protective listening behaviors of adolescent users of MP3 players and the association of these behaviors with demographic characteristics and frequency of use. METHODS. In 2007, 1687 adolescents (12-19 years of age) in 68 classes in 15 Dutch secondary schools were invited to complete questionnaires about their music-listening behaviors. RESULTS. Ninety percent of participants reported listening to music through earphones on MP3 players; 32.8% were frequent users, 48.0% used high volume settings, and only 6.8% always or nearly always used a noise-limiter. Frequent users were >4 times more likely to listen to high-volume music than were infrequent users, and adolescents in practical prevocational schools were more than twice as likely to listen to high-volume music as were those attending preuniversity education. CONCLUSIONS. When using MP3 players, adolescents are very likely to engage in risky listening behaviors and are unlikely to seek protection. Frequent MP3 player use is an indicator of other risky listening behaviors, such as listening at high volumes and failing to use noise-limiters. Copyright © 2009 by the American Academy of Pediatrics.