Although stalking is a widespread phenomenon that can be caused by different motives, consideration of the psychopathological underpinnings of stalking behaviour is scarce. In rare cases, stalking can be an expression of mental disorder. Psychotic stalking, for example, can occur as a symptom of schizophrenia or erotomania. Psychotic stalkers are criminally not responsible for their acts and have to be treated in a psychiatric hospital. The majority of stalkers, however, do not suffer from a disorder in need of treatment, and therefore their criminal responsibility is not diminished. Although legislative approaches to protecting victims of stalking differ widely in the European Union, mentally not severely disturbed stalkers can be prosecuted and punished according to criminal law in most countries. In some cases, the differentiation between mentally sane and mentally disturbed stalkers is difficult. This paper focuses on the psychopathology of such 'borderline cases', using the example of a court decision in Germany. Copyright (C) 2011 S. Karger AG, Basel