1. 1. Fat embolism can be demonstrated pathologically in about 50 per cent of fatal injuries, especially in closed fractures of the tibia and femur. In about 25 per cent of these cases it is a contributing cause of death. 2. 2. Clinically, fat embolism is not common but the diagnosis can be established on the basis of characteristic signs and symptoms and can be confirmed by x-ray and laboratory data. 3. 3. In occasional patients dramatic improvement with recovery may follow use of high concentrations of oxygen.