The authors investigated the intergroup processes of male adolescents within the context of social identity theory (SIT; H. Tajfel, 1978; H. Tajfel & J. C. Turner, 1979). The participants were English male adolescents (age = 14-15 years). They estimated in-group and out-group musical preferences and evaluated the in-group and out-group along a series of scales. The results showed in-group favoritism effects along the musical preference and evaluative dimensions. The participants reported greater liking for the in-group. Compared with the out-group, they associated the in-group more with positively stereotyped music and less with negatively stereotyped music. Compared with the out-group, they rated the in-group as more fun, more masculine, more sporty, less boring, less snobbish, and less weird. The participants with lower levels of self-esteem showed greater differentiation between groups and greater derogation of the out-group. The results supported the predictions of SIT and demonstrated the applicability of SIT for the study of adolescent behavior.