Expert testimonies and judges of 224 lawsuits of the years 1991 to 2001, who lead to the order of Preventive Detention in the German federal states of Bavaria, Brandenburg, Northrhine Westfalia and Saxony were analysed. Offenders with the order of Preventive Detention have mostly committed violent and/or sexual offences. Nearly two third of the inmates show personality traits with relevance for psychiatry or even personality disorders. Thus the discrimination between forensic psychiatric measurements and preventive detention is difficult. The quality of forensic psychiatric reports does not reflect the complexity of this task. They show diagnostic and prognostic weaknesses.