Psychiatric assessment and treatment of aggressive mentally ill offenders is one of the most difficult tasks in forensic psychiatry. Whereas psychiatric literature mostly refers to a uniform definition of aggression, different forms of aggression have been shown in animal experiments. In this study it was tested, whether a psychopathological differentiation of aggression was possible in men. In 124 individuals accused of homicide a preliminary dichotomic differentiation into undercontrolled and overcontrolled types of violent offenders (Megargee 1984) was examined. 60% of the population could be assigned to one of the two types. Undercontrolled individuals reacted violently when overburdened by situational conflicts. This form of aggression was called asthenic aggression. It was significantly more frequent in the mentally ill and led more often to the conclusion of diminished responsibility. In the undercontrolled offender aggression served mostly to achieve immediate goals. This form of violence was called sthenic aggression.