The subjects of this study are prisoners who were hospitalized from custody in a psychiatric clinic. All of such patients of one psychiatric clinic during the period from 1976 till 1978 were compared with a random sample of other psychiatric patients using case reports and other data. Differences were found concerning social, personal, psychiatric, and criminal history as well as psychopathological state and diagnosis. Compared to the complete population of prisoners of the area, prisoners from solitary confinement (mostly remanding custody) were overrepresented. Other risk factors for psychiatric hospitalization of prisoners are described. The results are discussed from prophylactic, therapeutic, and humanitarian points of view.