School bullying, the most prevalent type of school violence, is known to be related to various behavioral, emotional, and social problems both in victims and perpetrators. The purpose of the present study was to review available reports on school bullying in Korea and other countries, and author's two recently conducted epidemiological studies in a Korean community sample of elementary and middle school students. Among a total of 532 students of 4th to 6th graders of two elementary schools, 44.4% of students experienced school bullying. Children who were involved with school bullying reported impaired quality and satisfaction of friendship. Social immaturity, withdrawal, inattention-passivity, conduct problems, aggression, and male gender were associated with both victims and perpetrators of school bullying. In a 8-month prospective study of two middle schools, the prevalence of school bullying was similar to those in elementary schools (40.9~45.5%). Risks for chronic self-injurious/suicidal behaviors were significantly increased in chronic victims, perpetrators, and victim-perpetrators compared to those who were not involved with school bullying. Additionally, the male gender, first child, and extreme socioeconomic status were identified as environmental risk factors of school bullying. School bullying is very common among Korean elementary and middle school students. Both victims and perpetrators had more significant psychopathology than their counterparts. More active and scientifically tailored intervention and preventive programs are required to decrease school bullying and to provide appropriate assistance for promoting healthy development of Korean students.