The study analyzed data from a representative sample of 15,686 students in grades 6 through 10 in public and private schools throughout the United States who completed the World Health Organization's Health Behavior in School-aged Children Survey during the spring of 1998. The survey obtained self-reports of involvement in bullying and being bullied by others. A total of 29.9 percent of the sample reported moderate or frequent involvement in bullying, as a bully (13 percent), one who was bullied (10.6 percent), or both (6.3 percent). Males were more likely than females to be both perpetrators and targets of bullying. The frequency of bullying was higher among 6th through 8th grade students than among 9th and 10th grade students. Perpetrating and experiencing bullying were associated with poorer psychosocial adjustment; however, different patterns of association occurred among bullies, those bullied, and those who both bullied others and were bullied themselves. The study concludes that the prevalence of bullying among U.S. youth is substantial. Given the concurrent behavioral and emotional difficulties associated with bullying, as well as the potential long-term negative outcomes for these youth, the issue of bullying merits serious attention, both for future research and preventive intervention. 4 tables and 43 references