Since Virchow introduced the doctrine of thromboembolism almost 120 years ago, “few conditions in medicine have been subjected to so much analysis with so little elucidation” (33). Indeed, the causes and exact frequency of pulmonary embolism remain uncertain. The majority of such emboli arise from veins in the lower extremities and pelvis, and important predisposing factors are trauma, congestive heart failure, phlebitis and immobility. The clinical features of pulmonary embolism are protean. They depend in part on the number and size of the emboli, the presence or absence of pulmonary infarction and the nature of any underlying disease (s). Dyspnea without orthopnea and pleuritic chest pain are important symtoms, and tachycardia and fever are common signs. If one waits for hemoptysis, cough, pleural friction rub or radiographic abnormalities to develop, most cases of pulmonary embolism will go undiagnosed. Roentgenograms of the chest in patients with pulmonary embolism or infarction show an extremely varied picture, and no radiologic finding is diagnostic. Similarly, the electrocardiogram may demonstrate no ab-normality or any one or more of a variety of changes. The differential diagnosis includes respiratory, cardiac, neurologic, psychiatric and upper abdominal disorders. Of these, myocardial infarc-tion and pneumonia are the most important and the ones with which pulmonary embolism and infarction most likely are to be confused. The ideal treatment of pulmonary embolism is prevention of the initial thrombus formation. Methods ordinarily employed to accomplish this are early, full ambulation, the use of elastic stockings and anticoagulant therapy. Once pulmonary embolism has occurred, the therapy will depend on the available facilities, the type(s) of associated disease and the physician's skill. Supportive measures always are indicated and often are sufficient. Anticoagulants are used frequently. In some patients with pulmonary embolism, surgical therapy is indicated, either for the prevention of further embolism or for the resuscitation and treatment of the patient with massive embolism. Among those procedures in the former category, ligation of the superficial femoral veins has been used extensively for many years. Now it is much less popular because of the high incidence of recurrent pulmonary emboli following such an operation. Venous ligation at the level of the inferior vena cava effectively prevents further pulmonary embolism, but the incidence of unfavorable sequelae following operation is higher than in those with more distal ligations. It generally is agreed that the inferior vena cava should be ligated in the presence of septic thrombophlebitis, failure of anticoagulants or contraindications to anticoagulation in patients with pulmonary embolism. Technics of inferior vena caval occlusion vary somewhat with the preference of the operator, and in recent years several ingenious procedures have been suggested in order to prevent the passage of large pulmonary emboli and at the same time maintain the flow of blood through the inferior vena cava. Pulmonary embolectomy for the treatment of acute massive pulmonary embolism was suggested by Trendelenburg more than 50 years ago. However, so few patients survived the procedure that the Trendelenburg operation was discarded almost completely. Recent experience with pulmonary embolectomy using temprary cardiopulmonary bypass has resulted in the survival of more than one third as many patients in 2 years as survived the procedure without cardiopulmonary bypass during the previous half-century. In certain instances, partial cardiopulmonary bypass from the femoral vein to the femoral artery for resuscitation should be employed prior to definitive embolectomy. The technic of embolectomy consists of an arteriotomy in the main pulmonary artery during total cardiopulmonary bypass followed by manual compression of both lungs in conjunction with extraction of the emboli through the pulmonary arteriotomy. Further improvements in the technical aspects of pulmonary embolectomy are foreseeable, and extensions of the procedure into other areas of pulmonary embolism should be forthcoming.