Youth exposed to disasters experience stress and adjustment difficulties, which likely influence their interactions with peers. In this study, we examined changes in bullying and peer victimization in two cohorts of children. Youth from an area affected by Hurricane Katrina were assessed preand postdisaster (n = 96, mean [M] = 10.9 years old, 53% female), and a comparison group from a nearby area was assessed over the same time interval 1 year prior (n = 120, M = 10.2 years old, 52% female). Within the hurricane group, relations between symptoms of post-traumatic stress disorder (PTSD) with bullying and victimization also were examined. Following the hurricane, the hurricane group reported increased relational and overt bullying relative to the nonhurricane group, and PTSD symptoms predicted increased victimization. Thus, school personnel should be vigilant and prepared to respond to increased bullying following disasters and for increased victimization in youth experiencing PTSD symptoms. C 2009 Wiley Periodicals, Inc.Hurricane Katrina caused one of the worst natural disasters in U.S. history, and exposure to disasters such as Hurricane Katrina has been linked to psychological and behavioral difficulties in youth (Khoury, Warheit, Hargrove, Zimmerman, Vega, & Gil, 1997;Shaw et al., 1995;Swenson, Saylor, Powell, Stokes, Foster, & Betler, 1996;Weems, Pina, Costa, Watts, Taylor, & Cannon, 2007). Yet little research has examined how disasters and the resulting distress impact children's peer interactions, even though peers play an important role in children's postdisaster adjustment . Drawing from social dominance theory (e.g., Pellegrini & Bartini, 2001), the current study examined changes in predisaster bullying and peer victimization rates following Hurricane Katrina, relative to changes in a nonhurricane exposed comparison group. Additionally, drawing from a theoretical model whereby disaster-related distress negatively impacts psychosocial and behavioral functioning (Warheit, 1988), the associations between symptoms of post-traumatic stress disorder (PTSD) with children's bullying behaviors and peer victimization experiences, while controlling for prehurricane functioning, were also examined.Previous research suggests two primary processes whereby large-scale disasters might impact bullying and peer victimization rates among youth. First, social dominance theory suggests that when peer groups are in a period of transition, bullying and peer victimization rates will increase as youth try to establish and maintain dominance within the changing peer group (Pellegrini & Bartini, 2001). Although periods of peer group transition are normally thought to occur when youth from several elementary schools transition to a larger junior high or during the transition from junior high to high school, disasters often force large numbers of people to relocate. Thus, the influx of new students in schools around a disaster area likely increases overall rates of bullying and victimization as youth struggle to establish or maintain...