An ecological approach to bullying prevention is critical for the reduction of bullying and victimization. Any intervention implemented in a school to reduce bullying should include a variety of targets on all levels of the ecology and these interventions need to be sustainable by the school following introduction of the intervention. Schools are more aware today that bullying victimization causes harm to all those involved. Victims of school bullying suffer from increased mental health problems, perpetrators of bullying are more likely to enter the legal system and school communities have a more negative school culture that makes it harder for students to learn. States are requiring schools to be more accountable for eliminating bullying in school and schools respond by implementing research-based bullying prevention programs. The Olweus Bullying Prevention program has demonstrated effectiveness in elementary schools yet has limited research on its effectiveness in high schools. Considerable research has demonstrated the effectiveness of Olweus Bullying Prevention program in reducing bullying, victimization and other school related problems. However, less is known about the program's impact to reduce bullying behaviors in high school settings. The present study aimed at evaluating the Olweus Bullying Prevention program in a high school setting. Two high schools in the Midwestern region participated in the study with one school as the experiment school by implementing the Olweus program during one academic year. 699 students completed the Olweus Bully/Victim questionnaire at the beginning and end of the school year. The within group repeated design was employed to investigate the pre and post implementation difference and the MANOVA was performed to compare the differences in bullying and victimization between control and experimental school. The results showed no statistically significant effect of the intervention for reducing bullying others or bullying victimization. There was a slight reduction in bullying victimization in "hot spots" but this was not statistically significant. The possible reasons for failing to find any significant differences were discussed in relation to the ecological fitness of any prevention and intervention programs. The implications from the findings of this study illustrated the importance of supportive local administration and staff members in successful implementation of Olweus program It is equally important for Olweus trainers create a favorable working relationship with school administration and the bullying prevention coordinating committee, assess the school's readiness to implement the program, help the school address these issues prior to implementation. During the intervention period, it is critical that a variety of interventions are implemented on all levels of the school's ecological system. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]