The relationship between suicide attempts and different vulnerability factors was investigated in 61 male subjects during forensic psychiatric examination. Personality traits and psychopathy were determined by means of the Karolinska Scales of Personality (KSP) and the Psychopathy Checklist-Revised (PCL-R). Clinical diagnoses were determined by the use of Structured Clinical Interview for DSM-III-R (SCID). Platelet monoamine oxidase (MAO) activity was investigated in 58 subjects. Suicide attempters had extremely low socialization and high impulsive aggression. This was independent of a history of repeatedly criminal violence or not. They had higher PCL-R scores and lower levels of platelet MAO activity than non-attempters. No relationship was found between suicide attempts and repeated violent criminality. However, among the subjects with repeated criminal violence there was a highly significant difference between suicide attempters and non-attempters, indicating different personality profiles in violent offenders with and without suicidal behavior. Suicidal behavior was significantly associated with borderline personality disorder, but not with any other single DSM-III-R disorder. The results show a far more severe personality disturbance in suicide attempters than in other violent patients in this type of population. Suicidal behavior should therefore be evaluated and treated per se.