A statistical analysis was made of 890 casualties which occurred in mental institutions coming under the jurisdiction of the Department of Mental Health during 1942. Significant observations included:1. The casualty rate was highest among the aged.2. The casualty rate was highest in the senile psychoses and lowest in dementia præcox. The incidence was 10 times greater in the senile group than in dementia præcox.3. The most common causes for injury were slips, stumbles, etc., and these predominated in older patients. The next commonest cause was altercations which occurred in the younger age groups.4. Two-thirds of the accidents occurred on the wards.5. The peak of the casualty incidence occurred shortly after rising and appeared related to the routine of rising and preparing for the new day.6. Resulting from the 890 casualties there were 903 separate injuries recorded, 722 of which were fractures, with 532 involving the extremities, 168 of which were located in the femur. The mortality rate of the latter was in direct proportion to the age of the victim.Suggested methods for decreasing or preventing casualties were discussed.