A prospective study of post-traumatic fat embolism among a group of Chinese patients suffering from fractures demonstrated an incidence of 8.75% in fracture patients with overt clinical features and a mortality rate of 2.5%. In a multiple-fracture group the incidence of fat embolism was 35%. The significant findings of 64% of the patients with a low arterial pO2 and 52% with positive cryostat tests for fat globules suggested a high incidence of subclinical presentation. The presence of large vacuoles in the cryostat sections is demonstrated and its significance discussed. The 'iceberg' phenomenon of fat emobolism syndrome should be well recognized, particularly in patients with multiple fractures.