Approximately 11% of a 1-year sample of psychiatric inpatients from a single catchment area engaged in assaultive behavior before admission to the hospital. Among schizophrenic, alcoholic, and organic brain syndrome patients, assaultiveness was linked to emotional turmoil, as manifested by agitation and anger. In contrast, male patients with other diagnoses showed assaultiveness in the absence of substantial emotional distress, and patients with affective disorders were unlikely to exhibit assaultiveness even when high levels of agitation and anger were reported. The findings suggest that assessment and treatment of violent behavior in psychiatric patients are primarily linked to the nature of the underlying psychopathology.