Aggressive behaviour of adolescents may be based either on an inborn personality structure, or cultivated by training, i.e. the character of punishment. It is encountered in children with organic disorders of the CNS or psychotic disease. A specific case is aggressive behaviour in communities, being found in particular in communities of boys. The authors describe a typical case of an aggressor and the typical profile of the victim. Psychiatric intervention involves psychotherapeutic treatment and influencing of the social and family which should be focused on possible aggressive behaviour.