In the present study, quantitative and qualitative data are presented to examine individual and contextual predictors of bullying and victimization and how they vary by age and gender. Two waves of survey data were collected from 2,678 elementary, middle, and high school youth attending 59 schools. In addition, 14 focus groups were conducted with 115 youth who did not participate in the survey. Changes in both bullying and victimization were predicted across gender and age by low self-esteem and negative school climate, with normative beliefs supporting bullying predicting increases in bullying only. Focus group comments provided insights into the dynamics of bullying, highlighting its connection to emergent sexuality and social identity during adolescence. Findings are discussed in terms of their implications for preventive antibullying interventions in schools. (Contains 3 tables.)