While adolescents comprise only 15 percent of the population, they commit approximately 25 percent of the serious crimes. The best predictor of later violent criminality is childhood criminality, and the earlier a child manifests a pattern of violent behavior the more extensive will be the violent criminal career. Serious delinquents report high rates of polydrug use, emotional and school problems, association with delinquent peers, and family problems. Other determinants of violent behavior may include attitudes toward violence, child abuse and other family violence, and individual psychopathology and neurological and biological impairment. Assessing the natural history and outcome of juvenile violence is difficult, because society usually intervenes in some form, therapeutic or not. Violent adolescents are difficult to treat. Negativism, disparagement, and deidealization are common in individual psychotherapy with these patients. If the adolescent is unable to sustain a treatment relationship, institutionalization may be necessary. Medication, such as neuroleptics, anticonvulsants, and propranolol, have been reported to be effective in controlling aggression in violent adolescents. Violent delinquents often are shunted out of the mental health system into the correctional system, however, the importance of psychological and personality factors in violent behavior should not be overlooked. 116 references.