In Belgium, the law of "social defense" stipulates that an accused "which is either in a state of dementia or in a serious state of mental disturbance or mental deficiency, incapable of controlling his actions" can be interned. The establishment of social defense (ESD) in Tournai (Belgium) hosts 350 inmates. OBJECTIVES: In collaboration with the Centre for research in social defense, we organized a systematic assessment of patients interned in ESD. This is the first study evaluating prospectively this population. METHODS: Of the total, 229 patients signed informed consent. Different scales of assessment (MINI, WAIS-III, SCID II) were used. Descriptive analyzes were applied (SPSS version 12). RESULTS: We show that 48.8 % of our participants had committed a sexual offense (rape or attempted rape, indecent assault, public outrage or mixed). The average intelligence quotient is 71.4. According to the MINI, 33.2 % of participants showed no psychiatric disorder. Among psychiatric disorders, psychotic disorders are the most represented (37.4 %). According to the SCID, personality disorders were absent in 26.8 % of our participants. Most of the axis II disorders are represented personality disorders related to cluster B (57.3 %) mainly with antisocial personality disorder (37.9 %). CONCLUSION: These data demonstrate the significant heterogeneity of our sample and the need for the establishment of specific care routes to each subpopulation.