In this study, 242 randomly selected male offenders who were receiving psychiatric treatment in prison were administered psychological and neuropsychological evaluations and were followed during their treatment in a prison psychiatric hospital. Offenders who harmed themselves in treatment were compared to those who did not harm themselves. Eighteen percent of offenders harmed themselves, the severity of which required medical intervention. Young age, drug abuse, absence of Axis I mental disorder but presence of Axis II borderline personality disorder identified offenders who harmed themselves. Psychopathy checklist-revised (PCL-R) total rating > or = 30 and PCL-R Factor 2 (antisocial lifestyle) rating also identified offenders who harmed themselves. Additionally, offenders who harmed themselves also were 8.36 times more likely than their cohorts to harm treatment staff. Theoretical understanding of offenders who harm themselves, the importance of considering the environmental context in identifying risk factors for self-harm, and implications for treatment are suggested.