Examined roles for attitudes about violence as a possible influence on the frequency of commonplace aggression toward peers among 1,033 adolescents in the 7th through 9th grades. The peer victimization measure adapted from prior studies yielded 2 reliable subscales: Victimization of Self and Victimization of Others. The attitudes and beliefs measure modified for this study yielded 3 reliable subscales (Aggression Is Legitimate and Warranted, Aggression Enhances Power and Esteem, One Should Not Intervene in Fights). These attitudes were meaningfully related to self-reported aggression toward peers but less clearly related to self-victimization. The attitudes were plausible mediators of the relation between gender and aggression toward others and appeared influential for both boys' and girls' aggression toward peers. Little support was found for these attitudes moderating the relation between self-victimization and aggression toward others, yet a clear link between victimization of self and aggression toward others was evident. Results support an emphasis on attitudes and values regarding aggression in violence-prevention efforts, as well as direct efforts to reduce self-victimization.