Identifying factors buffering the bidirectional relationship between bullying victimization and perpetration is crucial in informing interventions to protect students from cycling between being bullied and bullying others. Nevertheless, that bidirectional relationship and its buffering factors have been underexamined among children. As a potential buffer of the bidirectional relationship, the researcher focused on children's positive peers guided by an integrative framework of dominance, homophily, and opportunity theories. Accordingly, the researcher aimed to (a) test the bidirectional relationship between bullying victimization and perpetration among U.S. children and (b) examine positive peer affiliation as a buffer of that bidirectional relationship. Using data from the fourth- and fifth-grade rounds of the Early Childhood Longitudinal Study, Kindergarten Class of 2010-2011 (ECLS-K:2011), the researcher tested a structural model in which bullying victimization and perpetration are bidirectionally related (Hypotheses 1 and 2); and positive peer affiliation buffers the relationship between bullying victimization and later perpetration (Hypothesis 3) and the association between bullying perpetration and subsequent victimization (Hypothesis 4). The model was specified based on the latent cross-lagged panel model (CLPM) and the latent moderated structural equations (LMS) method to control for prior levels of the outcome variables and produce latent interaction terms. With an adequate model fit, results confirmed Hypotheses 1, 2, and 3. However, findings did not support Hypothesis 4, indicating positive peer affiliation as a significant enhancing moderator, not as a buffer, of the relationship between bullying perpetration and later victimization. Current findings suggest that antibullying interventions might focus on helping children who are bullied be affiliated with positive peers to prevent their subsequent bullying behavior. Supporting positive peer affiliation may also be beneficial with regard to preventing children from bullying victimization unless they are engaging in bullying very often. Professionals should pay special attention to children who frequently bully and, at the same time, are affiliated with positive peers, considering such children to be at the highest risk of being victimized by bullying. Limitations of this study and future research directions are discussed. [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://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]