The inmates were receiving psychiatric treatment in a mental health facility located within a California State prison. Data from two consecutive studies were analyzed. The ages of participants ranged from 18 to 65 years, with a mean age of 33 years. Education ranged from third grade to postgraduate. Thirty percent of the inmates were diagnosed with a psychotic disorder, 10 percent with a mood disorder, 12 percent with an "organic" disorder, and 14 percent with disorders characterized by both psychotic and mood features. Using record reviews; interviews; and neuropsychological, Rorschach, and psychopathy measures, risk factors were identified for assault in prison and in prison psychiatric treatment. A total of 153 of the inmates had committed an assault in prison, and 20 committed assaults while in psychiatric treatment. Assault was defined as a "serious rule violation" that involved use of force or violence against another person. All assaults were against either correctional or mental health staff. The study found that California Youth Authority placement, inhalant use, antisocial lifestyle, neurological injury, neuropsychological impairment, and higher PCL-R Factor II ratings were associated with assault in prison. The absence of major mental disorder, neurological impairment, or psychotic thinking, but the presence of psychopathy were associated with assault while in prison psychiatric treatment. In addition, the following issues are important in addressing the risk for violence: the context in which violence occurs, the need for clear admission criteria for prison psychiatric treatment, and the need to develop risk assessments that are specific to prison environments. 6 tables, 2 figures, 22 references, and appended Violence Rating Scale and a listing of prison offenses