Analysis of hospital mortality showed that thromboembolism of the pulmonary artery was a cause of lethal outcomes in thoracic surgery in 0.4% of hospitalized patients, in 0.7% of those who underwent operation, in 14.8% of all patients who died, and in 15.6% of those who died in the postoperative period. The principal causes of death in thromboembolism of the pulmonary artery were various diagnostic errors (79.5%), severity of the patient's initial condition (14.1%), and defective treatment (6.4%). Prevention of thromboembolism of the pulmonary artery is based on timely detection of its sources by wider use of ultrasonic and radionuclide methods, rarer application of invasive diagnostic methods, and the use of anticoagulant therapy after operations in the risk groups.