The study was based on the self-reports of 885 Norwegian adolescents aged 13- to 15-years-old. The psychosocial factors were represented by an average of scores on 3–12 single items, each with 5 possible response categories. Bullying behavior was defined as bullying other pupils sometimes or more often during the term. The prevalence of bullying behavior was 9.2 percent, but significantly higher among boys than girls. Odds ratios of bullying behavior according to psychosocial factors were calculated in a multiple logistic regression analysis. Although personality traits were important in explaining the problem of bullying behavior, an important finding in the present study was that environmental factors, or at least the pupils’ perception of the environment, also seemed to be associated with bullying behavior. An increasing risk of bullying was observed with an increasing degree of school alienation. School alienation, in this study, represented the degree to which pupils experienced work at school as meaningless and unchallenging. One intervention strategy against bullying could be to establish learning activities that the pupils find more personally challenging. The result for general self-efficacy beliefs, although mainly pronounced for pupils at grade level eight, showed that the typical bullies did not have poor self-esteem and that a high level of self-esteem was associated with aggressive behavior. Perceived social support from the teacher as well as peers was associated with lower odds of bullying behavior. No significant association was seen with decision control. 3 notes, 3 tables, 36 references