More than other disciplines in medicine psychiatry is closely connected with legal and medico-legal issues. Mental disorders can influence the individual capacities of cognition and affectivity which are necessary to comply with social norms and rules. Disturbances of impulse control, affect regulation and reality control may lead our patients to aggressive, disruptive, or disorganized behaviours which result in different forms of conflicts with the law. The psychiatrist must be able to detect the influence of disturbed mental functioning in offenders and to protect his patients against the usual consequences in society for deviant and criminal behaviour. Mentally ill offenders need treatment, not punishment. This is the reason that we need a well developped subdiscipline of forensic psychiatry. Important tasks are the evaluation of legal responsibility, the treatment and rehabilitation, last not least the prognosis of dangerousness. In addition, forensic psychiatry is based on detailed and differentiated analysis of abnormal mental conditions including psychopathic behaviours. Therefore, this subdiscipline is a resort for general and for clinical psychopathology, which have lost some of their importance in other fields of psychiatry