Records of postmortem examinations at the Mayo Clinic for the last ten years show that pulmonary embolism occurred in 313 cases; in 267 of these, the complication followed operation and in 46, it occurred in nonsurgical cases. In 223 (83.5 per cent) of the 267 cases, emboli were the primary cause of death, and in 44 (16.5 per cent), they were either contributory factors or were so small that they had little or no connection with the patient's death. One hundred and four of the patients who died from embolism were men and 119, women; their average age was 53.2 years. The average age of 1,000 adult patients operated on consecutively was found to be 42.8 years. Therefore, the average age of the patients dying from embolism was 10.4 years greater than that of the average patient coming to operation. The average height for these patients was 5 feet, 6.5