The problem of recurrent pulmonary embolism in its varied clinical forms presents a challenge in recognition and management. Despite "adequate" anticoagulant therapy recurrent embolism is apt to occur either during anticoagulant therapy or after the completion of treatment.1 Femoral vein ligations have been reported to be of little value in obviating pulmonary embolism.2,3 Vena caval ligation, despite its sequelae, has proved to be the most effective tool in the prevention of recurrent pulmonary embolism. The purpose of this paper is to present a clinical analysis of recurrent pulmonary embolism as seen at the Duke University Medical Center since 1950. Corollary physiologic studies in patients with thromboembolic disease undergoing vena caval ligation will also be outlined. Clinical Analysis of Cases Since 1950, we have studied 416 patients with pulmonary embolism seen at the Duke University Medical Center. Of these, 109 had definite clinical evidence of recurrence as judged by