The frequency of sudden death from massive pulmonary embolism in the patient who has successfully passed through a major surgical operation or is recuperating from an injury, the recent parturient and the person with cardiac disease or phlebitis warrants a consideration of this condition. The incidence of fatal pulmonary embolism may be seen from the following figures: In our own small series, the basis of this communication, 5 deaths were post-traumatic, 5 followed medical treatment, 13 were postoperative and 1 was postpartum. The cases were observed in 1,781 consecutive unselected autopsies on adults from Jan. 1, 1926, to Oct. 31, 1937. The material came from general hospitals and from the coroner's service. A study of our own material and a survey of the literature indicate the importance of the following three points: 1. The increased risk of this complication for certain persons and with certain types of operation. 2. The