This study evaluated the clinical correlates and inpatient course of self-mutilation in a diagnostically diverse sample of hospitalized forensic patients. Fifty-three male forensic inpatients, treated in a maximum-security hospital, who engaged in at least one instance of self-mutilation during a 2-year period, were studied and compared with 50 male forensic patients at the same hospital who had not engaged in self-mutilation. Self-mutilating patients were younger, more likely to carry a diagnosis of personality disorder or mental retardation, engaged in more outwardly directed aggressive behavior as assessed by the Overt Aggression Scale, were treated with substantially higher doses of neuroleptics, and were more likely to be civil or correctional patients than insanity acquittees. The two groups did not differ on variables such as history of suicide, history of violence, neurological characteristics, and other demographic variables. After an incident of self-mutilation, the probability of recurrence was high. The substantially higher level of outwardly directed aggression of self-mutilating patients, along with their higher apparent need for neuroleptization and the high risk of recurrence of the self-mutilation, suggest that they are a subset of violent individuals who are relatively unresponsive to treatment and who are dangerous to self and others.