Self-harm was defined as any self-inflicted action that resulted in injury requiring medical attention. Eighteen percent (n=43) of the 242 randomly selected offenders in the study sample harmed themselves while in psychiatric treatment. Young age, Axis II borderline personality disorder, and psychopathy with elevated Factor 2 (antisocial lifestyle) ratings on the Psychopathy Checklist-Revised significantly identified inmates who harmed themselves while in psychiatric treatment. Inmates who harmed themselves were also 8.36 times more likely than their cohorts to harm treatment staff. The 242 male inmates were receiving psychiatric treatment in a mental health facility within a California State prison. The average length of treatment for all participants was 117 days. Demographic information was obtained through interviews and a review of official records. The sample was evaluated for neuropsychological functioning and psychiatric diagnosis. A Rorschach evaluation was also conducted. These findings suggest two primary implications for mental health professionals who are treating mentally ill offenders. First, in evaluating risk factors for self-harm while in psychiatric treatment, it is important to consider the context in which self-harm occurs. Second, self-harm behavior should be considered a "failure of inhibition," and treatment should focus on this problem. 4 tables, 1 figure, and 46 references