Prediction of in-patient psychiatric violence is difficult: longitudinal appraisal during environmental change may identify Influential factors. Incidents on a secure ward fell substantially in number and severity over 31 months during which staff were trained in control and restraint techniques (CAR) and a monthly audit of incidents was carried out. A few patients caused many incidents. Women were disproportionately violent: both sexes preferred a victim of the same gender. Most incidents occurred in clusters by the same patient. Perceived antecedents were patients' psychosis, inadequate CAR and other staff. Increasing C&R staff was the only factor associated with reducing violence. Patients attacked each other rather than nurses as violence decreased.