The subject of pulmonary embolism is assuming ever-increasing importance, not only medically but legally. More than ever, the physician should have basic knowledge of the pathophysiology. This article outlines the modern concepts of the mechanisms involved and the etiologic factors. Pulmonary embolism is often difficult to diagnose. A thorough history and ph,ysical examination are fundamental, but there are several good diagnostic aids in the field of radiography, angiography, thermography, lung scanning, ultrasonic procedures, and enzyme and pulmonary function tests. Modern medical treatment is outlined-including preventive therapy, the treatment of shock, and the use of anticoagulants and thrombolytic agents. Surgical techniques include some ingenious new methods. However, the best results are obtained when surgical skill is eombined with good judgment in the.proper selection of cases.