There are many problems posed by aggressive youth, the harm to victims and the loss of young people into the criminal justice system and penal confinement. Aggression Replacement Training (ART) was developed by Arnold Goldstein and his colleagues as a means of working with aggressive young people to help them learn new, prosocial ways of behaving. This paper looks at the theory and the research that underpins the three constituents of ART--skills training, emotional control training, and moral reasoning training. It is shown that ART has a solid theoretical base and that the research evidence favours this type of approach to working with young people.