Violent behavior is a significant problem in psychiatric hospitals. The authors reviewed hospital incident reports to identify the characteristics of violent behavior in a large state psychiatric hospital. They found that a very small percentage of patients accounted for a majority of violent episodes, that rates of violent behavior varied among hospital units, that assaultive behavior was more common than self-harm in the long-term units, and that most commonly the assault victims were other patients. The data support earlier studies demonstrating that a small number of patients are responsible for a majority of violent episodes in a hospital setting.