The Study Group on Serious and Violent Juvenile Offenders (SVJ) collaboratively examined the current research on risk and protective factors, the development of SVJ offending careers, and effective prevention and intervention programs for these offenders. The study group found that most SVJ offenders are male and usually display early minor behavior problems that lead to more serious delinquent acts. The majority of SVJ offenders tend to have multiple problems such as substance abuse and mental health difficulties in addition to school problems. Also, SVJ offenders are disproportionately victims of violence themselves. The research shows that there are effective treatments for many delinquent juveniles, both in the community and in institutional settings. Focusing on early intervention with children who may be at risk for delinquent behavior is crucial. Comprehensive community intervention efforts are most effective. A program of research on the causes and correlates of delinquency shows that childhood maltreatment is associated with later behavior problems; less serious problem behavior precedes more serious delinquency; serious delinquents have many co-occurring problems; very young children are involved in serious violent behavior; and violence among girls has increased. These findings suggest that early identification and treatment are important, particularly when the maltreatment of children is involved. Parents, schools, mental health practitioners, and the juvenile justice community must cooperate to screen and treat children at risk of developing serious disruptive behaviors.